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nnd  compact  statement,  the  elements  of  this  important  brand 
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Sheldon  &  Company's   '2'ext-53ooks. 
SHAW'S   NEW   SERIES 

ON 

ENGLISH  AND  AMERICAN  LITEEATURE. 


I. 

Shaw9 s  Neiv  History  of  English  and  American  Lit' 
erature.  This  book  ha&  been  prepared  with  the 

greatest  care  by  Prof.  TRUMAN  J.  BACKUS,  of  Vassar  College, 
using  as  a  basis  Shaw's  Manual,  edited  by  Dr.  WILLIAM  SMITH. 
The  following  are  the  leading  features  of  the  book  : 

1.  It  has  been  put  into  the  modern,  text-book  fonn. 
id.  It  is  printed  in  larye,  clear  type. 

3.  Many  parts  of  the  book,  which  were  not  very  clear,  have  been  entirely 
rewritten. 

4.  The  history  of  yreat  Authors  is  marked  by  the  use  of  larger-sized 
type,  which  indicates  to  the  scholar  at  once  the  important  names  iu  English 
and  American  literature. 

5.  It  also  contains  diagrams,  showing  the  easiest  way  to  classify  and 
remember  the  eras  in  English  literature.     \Ve  believe  that  this  is  the  best 
text -book  on  this  important  subject  ever  offered  to  the  American 
public. 

II. 

Shaw's  Specimens  of  American  Literature,  and 
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N.  MARTIN,  D.D.,  L.H.D.,  Professor  in  the  University  of  the  City 
of  New  York.  1  vol.  12mo. 

This  book  contains  specimens  from  all  the  chief  American  writers.  Espe- 
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style. 

As  a  LITERARY  READER  for  use  in  our  Higher  Seminaries,  it  is 
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III. 

Shaw's    Choice   Specimens    of   English   Literature. 

A  Uompanion  Volume  to  the  New  History  of  Literature.  Selected 
from  the  chief  English  writers,  and  arranged  chronologically  by 
THOS.  B.  SHAW  and  WM.  SMITH,  LL.D.  Arranged  and  enlarged 
for  American  students  by  BENJ.  N.  MARTIN,  D.D.,  L.H.D.,  Prof, 
of  Philosophy  and  Logic  in  the  University  of  the  City  of  New 
York.  1  vol.  large  12mo. 

We  shall  still  continue  to  publish 

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'/fff. 


ELEMENTS 


OF 


C  H  E  M  ISTRY 


A  TEXT  -  BOOK  I  F(M ;;  SCHOOLS. 


BY 

ELROY    M.    AVERY,    PH.D., 

AUTHOR  OF  ELEMENTS  OF  NATURAL  PHILOSOPHY,  ETC. 


ILLUSTRATED    BY    NEARLY    200  WOOD    ENGRAVINGS. 


NEW     YORK 

SHELDON  &  COMPANY, 

No.   8    MURRAY    STREET. 

1881. 


IN  MEMORIAL 


DR.    AVERY'S 
PHYSICAL   SCIENCE   SERIES. 


I  St. 

THE    ELEMENTS   OF    NATURAL    PHILOSOPHY. 

-  •    . 

•   • 

9\    • 


TEACHER'S    HAHD    BOOK. 

To   accompany    AVERY'S    NATURAL    PHILOSOPHY;   containing   Solutions   to 
Problems,  Additional  Experiments,   Practical  Suggestions,  etc. 


THE    ELEMENTS    OF    CHEMISTRY. 

4th. 
THE    HIGH    SCHOOL   CHEMISTRY. 

Containing  the  ELEMENTS  OF  CHEMISTRY,  with  additional  chapters  on 
Hydrocarbons  in  Series,  or  ORGANIC  CHEMISTRY.  It  can  be  used  in  the  same 
class  with  the  ELEMENTS.  (In  preparation^ 

5th, 

TEACHER'S    HAND    BOOK. 

To  accompany  Avery's  Chemistries. 

Copyright,  1881,  by  Sheldon  &  Co. 


Blectrotyped  by  SMITH  &  McDotiGAL,  82  Beekman  Street,  New  York. 


'T  PAVE  a  room  set  apart,  if  possible,  expressly  for 
-• — *-  chemical  operations.  It  is  generally  convenient  to 
have  this  laboratory  on  the  ground  floor,  for  convenience 
in  supplying  water  and  draining  off  the  waste.  This  room 
must  be  ivell  ventilated.  Secure  a  ventilating  chamber 
(App.  22)  for  the  laboratory,  and  a  ventilating  hood  con- 
nected with  the  chimney  flue  or  ventilating  shaft  for  each 
pupil,  if  you  can.  If  you  can  not  do  this,  keep  an  open 
fire  burning,  so  that  offensive  gases  and  vapors  may  be 
removed  from  the  room  as  well  as  possible  in  that  manner. 
Around  the  walls  of  the  room,  provide  working  benches  or 
tables,  about  75  cm.  (2-J-  feet)  wide.  Each  pupil  should  be 
allotted  about  a  meter  of  working  space  at  these  tables, 
and  7^/6?  responsible  for  its  condition.  If  the  building  is 
provided  with  gas  and  water,  run  pipes  around  the  walls, 
and  provide  each  pupil  with  a  gas  cock  and  a  water  cock, 
to  which  he  may  attach  flexible  tubing.  Over  the  benches 
place  narrow  shelves,  to  hold  the  chemical  reagents;  be- 
neath the  benches  place  shelves  or  drawers,  for  holding 
pieces  of  apparatus,  etc,  If  the  building  is  not  connected 


iv  TO    TEACHERS. 

with  a  regular  water  supply,  see  that  plenty  of  water  is 
always  at  hand  in  a  tank,  barrel,  or  in  pails.  A  small 
cook  stove  will  be  a  great  convenience. 

If  a  room  can  not  be  set  aside  as  a  laboratory,  flat  tables 
may  be  laid  upon  the  desks,  and  the  reagents',  apparatus, 
etc.,  kept  in  a  cabinet  or  cupboard. 

Of  course,  a  regularly  fitted  laboratory,  writh  further  and 
better  means  than  those  above  suggested,  is  desirable,  and 
should  be  provided,  when  means  can  be  secured  for  the 
purpose.  See  Prick's  Physical  Technics,  Chap.  I. 

The  chief  significance  of  the  foregoing  is  that,  as  far  as 
possible,  the  experiments  are  to  be  performed  by  the  pupil 
rather  than  for  him.  Make  careful  examination  of  the 
pupil's  notes,  seeking  to  lead  him  to  accurate  observation, 
intelligent  discrimination  between  essential  and  merely 
incidental  conditions  and  results  of  an  experiment,  as  well 
as  to  precision  and  conciseness  of  statement. 

Have  your  pupils  habitually  pronounce  the  full  name  of 
substances  symbolized  in  this  book.  For  example,  "  H20 
is  composed  of  H  and  0,"  should  be  read :  "  Water  is  com- 
posed of  hydrogen  and  oxygen." 

The  author  would  be  glad  to  receive  suggestions  from 
teachers  using  this  book,  or  to  answer  any  inquiries  they 
mav  make. 


TTAVE  a  place  for  everything,  and  keep  everything  in 
1 —  its  place,  when  you  are  not  using  it.  Clean  every 
utensil  or  piece  of  apparatus  when  you  have  used  it ;  never 
put  away  anything  dirty.  Cleanliness  is  a  necessity  in  the 
chemical  laboratory.  Ac  jiiire  the  habit  of  labeling  every 
chemical  that  you  put  away  or  leave  for  a  time,  writing 
the  name  or  the  chemical  symbol  in  easily  legible  char- 
acters. 

Before  beginning  an  experiment,  look  over  all  of  your 
preparations,  be  sure  that  everything  is  ready  and  within 
easy  reach,  or  you  may  suddenly  discover  a  need  for 
another  hand.  Be  sure  that  all  corks  and  connections  are 
well  fitted.  Place  your  materials  and  apparatus  at  your 
left  hand  and  lay  them  down  at  your  fight,  when  you  have 
used  them,  keeping  the  middle  of  your  bench  clear  for 
operating. 

Do  not  waste  even  inexpensive  material.  Be  sure  that 
you  know  wliy  you  do  a  thing  before  you  do  it.  Always 


VI  TO    THE    PVPTL. 

use  the  simplest  form  of  apparatus.  Do  not  think  that 
you  must  have  everything  just  as  described  by  the  author. 
If  a  Florence  flask  is  called  for  by  the  text-book,  and  you 
have  not  one,  you  may  be  able  to  get  along  with  a  bottle. 
A  hammer  is  not  wholly  necessary  for  the  driving  of  a 
nail,  although  it  may  be  desirable. 

Make  careful  notes  on  all  experiments  as  they  proceed. 
"The  scrap  of  paper  well  stained  with  acid  is  of  much 
greater  value  than  the  half  worked  out,  though  clean, 
notes  written  down  after  the  experiment  has  passed  away." 
These  rough  notes  should  subsequently  be  neatly  copied 
into  a  book,  the  mere  copying  of  the  observations  being  of 
great  help  in  remembering  them. 

Ever  keep  in  mind  the  fact  that  an  experiment  is  in- 
tended to  teach  something,  and  that  it  can  not  serve  its 
purpose  unless  it  is  accompanied  by  careful  observation  of 
the  effects  produced,  and  equally  careful  study  of  the  rela- 
tions borne  by  these  effects  to  the  conditions  of  the  exper- 
iment. 

Take  an  early  opportunity  for  a  careful  reading  of  the 
Appendix  to  this  book,  so  that  you  may  be  able  to  refer  to 
it  subsequently,  when  you  need  help  that  it  may  give. 

In  the  folio w.ing  pages,  the  specific  gravity  of  all  gases  is 
referred  to  hydrogen  as  the  standard.  All  temperatures 
are  recorded  in  Centigrade  degrees. 


PAGK 

TO   THE  TEACHER iii 

TO   THE   PUPIL v 

CHAPTER  I. 

THE    DOMAIN  OF  CHEMISTRY 1 

CHAPTER   II. 

WATER    AND    ITS   CONSTITUENTS. 

SECTION  I. — ANALYSIS  OF  WATEK 10 

"       II.— HYDROGEN 14 

III.— OXYGEN  27 

"       IV. — COMPOUNDS  OP  HYDROGEN  AND  OXYGEN .    ...  38 

CHAPTER  III. 

AIR   AND    ITS   CONSTITUENTS. 

SECTION  I. — AIR 45 

II.— NITROSEN 50 

CHAPTER  IV. 

SYMBOLS,   NOMENCLATURE,    MOLECULAR    AND   ATOMIC 

WEIGHTS..  53 


lll  CONTENTS. 

CHAPTER  V. 

COMPOUNDS   OF   HYDROGEN,    OXYGEN   AND    NITROGEN. 

PAGE 

SECTION  I.— AMMONIA 59 

"       IT. — NITRIC  ACID 65 

III.— NITROGEN  OXIDES 68 

CHAPTER  VI. 

QUANTIVALENCE,    RATIONAL   SYMBOLS,    RADICALS,..     74 

CHAPTER  VII. 

THE   HALOGEN    GROUP. 

SECTION  I.— CHLORINE 79 

II.— HYDROCHLORIC  ACID 87 

"      IIIN — OTHER  CHLORINE  COMPOUNDS  93 

"      IV.— BROMINE,  IODINE,  FLUORINE 97 

CHAPTER  VIII. 
STOICHIOMETRY 104 

CHAPTER  IX. 

THE   SULPHUR    GROUP. 

SECTION  I.— SULPHUR 110 

"       II.  — HYDROGEN  SULPHIDE 117 

III.— SULPHUR  OXIDES  AND  ACIDS 124 

"     IV.— SELENIUM  AND  TELLURIUM 187 

CHAPTER   X. 

ACIDS,  BASES,  SALTS.  Etc 140 

CHAPTER  XL 

BORON 147 


CONTESTS.  IX 

CHAPTER  XII. 

PAGE 

VOLUMETRIC   CONSIDERATIONS 151 

CHAPTER  XIII. 

THE   CARBON    GROUP. 

SECTION  I.— CARBON 155 

"       II. — SOME  CARBON  COMPOUNDS 160 

'•'     III.— SOME  HYDROCARBONS , , 177 

"     IV. — ILLUMINATING  GAS 188 

"      V.— SOME  ORGANIC  COMPOUNDS 194 

"     VI.— SILICON 201 

CHAPTER  XIV. 

THE   NITROGEN   GROUP. 

SECTION  I.— PHOSPHORUS 305 

"      II. — PHOSPHORUS  COMPOUNDS . .  .   211 

<;     III. — ARSENIC  AND  ITS  COMPOUNDS 217 

"     IV.— ANTIMONY,  BISMUTH,  ETC 222 

CHAPTER  XV. 

METALS   OF  THE  ALKALIES. 

SECTION  1. — SODIUM '. 229 

"      II. — POTASSIUM,  ETC 237 

CHAPTER  XVI. 

METALS   OF  THE  ALKALINE   EARTHS 246 

CHAPTER  XVII. 

METALS   OF  THE   MAGNESIUM    GROUP 252 

CHAPTER  XVIII. 

METALS   OF  THE   LEAD   GROUP..  .  258 


X  '  '<>. \TEXT8. 

CHAPTER  XIX. 

METALS   OF  THE  COPPER   GROUP. 

PAGE 

SECTION  I.— COPPER 263 

"       IL— SILVER 267 

"     III.— MERCURY 271 

CHAPTER  XX. 

METALS   OF  THE  ALUMINUM    AND    CERIUM    GROUPS..  275 

CHAPTER  XXL 

METALS   OF  THE   IRON   GROUP. 

SECTION  I.— IRON 279 

IL— STEEL 290 

"     III. — MANGANESE,  COBALT  AND  NICKEL.  295 

CHAPTER  XXII. 

METALS   OF  THE  CKROMIUM   GROUP 299 

CHAPTER  XXIII. 

METALS   OF  THE  TIN    GROUP 802 

CHAPTER  XXIV. 

METALS   OF   THE   GOLD    GROUP 306 

APPENDIX 315 

INDEX..  343 


THE     DOMAIN     OF    CHEMISTRY. 


1.  What  is  Matter? — Mattel1  is  anything  that 
occupies  space  or  "takes  up  room." 

Everything  discernible  by  any  of  our  senses  is  matter. 
Everything  that  has  weight  is  matter  ;  all  matter  has 
weight. 

2.  Divisions  of  Matter. — Matter  may  be  con- 
sidered as  existing  in  masses,  molecules,  and  atoms. 

Note.  —  The  word  molecule  is  from  the  diminutive  of  moles,  a 
Latin  word  meaning  a  mass.  Etymologically,  molecule  means  a  little 
mas,s.  .The  word  atom  is  from  the  Greek,  and  signifies,  etymology 
cally,  a  thing  that  can  not  be  cut  or  divided. 

3.  What  is  a  Mass  ? — A  mass  is  any  quantity  of 
matter  that  contains  more  than  a  single  molecule, 

Any  quantity  of  matter  that  can  be  appreciated  by  the 
senses,  even  with  the  aid  of  modern  apparatus,  is  a 
mass,  while  many  masses  are  too  minute  to  be  thus  appre- 
ciable. 

4.  What  is  a  Molecule?  —  A  molecule  is  the 
smallest  particle  of  matter  that  can'ejcist  l)y  itself , 
separate  from  other  particles  of  matter ;  or  it  is  the 
smallest  quantity  of  matter  into  which  a  mass  can  be  di- 
vided by  any  process  that  does  not  destroy  its  identity  or 
change    its  chemical  Mature,     Molecules  are  exceedingly 


2  THE  DOMAIN   OF  CHEMISTRY.  §  4 

small,  far  beyond  the  reach  of  vision  even  when  aided  by 
a  p-fruverful  microscope. 

/;  («,)  Acco_rdin£  to  one  of  the  best  authorities,  a  cubic  centimeter 
(Appomlnt  2}  <vf  £a's,  at  tlie  ordinary  atmospheric  pressure,  contains 
about  1,000,000,000,000,000,000,000,000  (=:1024)  molecules. 

(&.)  Natural  Philosophy  teaches  us  that  heat  is  one  kind  of  energy 
resulting  from  motion  (Ph.  §  473).  But  this  motion  of  a  hot  body, 
constituting  the  heat  of  the  body,  is  wholly  invisible.  The  motion 
pertains  to  "  parts  of  the  body  too  minute  to  be  seen  separately  and 
within  limits  so  narrow  that  we  cannot  detect  the  absence  of  any 
part  from  its  original  place.  We  are  to  have  the  conception  of 
a  body  consisting  of  a  great  many  small  parts,  each  of  which  is  in 
motion.  We  shall  call  any  one  of  these  parts  a  molecule  of  the  sub- 
stance.' A  molecule  may,  therefore,  be  defined  as  a  small  mass  of 
matter,  the  parts  of  which  do  not  part  company  during  the  excur- 
sions which  the  molecule  makes  when  the  body  to  which  it  belongs 
is  hot." 

(c.)  The  molecules  of  any  given  substance  are  held  to  be  exactly 
alike,  but  different  from  the  molecules  of  any  other  substance.  For 
example,  one  copper  molecule  is  exactly  like  every  other  copper 
molecule,  but  different  from  every  molecule  of  any  substance  that  is 
not  copper.  The  nature  of  the  substance,  therefore,  depends  upon 
the  nature  of  its  molecule. 

5.  What  is  an  Atom  ? — An  atom  is  the  small- 
est particle  of  matter  that  can  exist  even  in  com- 
bination. 

(a.)  Nearly  every  molecule  is  composed  of  two  or  more  atoms.  As 
we  shall  see,  some  molecules  are  very  complex.  The  common  sugar 
molecule  contains  forty-five  atoms. 

(&.)  An  atom  may  also  be  defined  as  the  smallest  quantity  of  an 
element  that  exists  in  any  molecule. 

6.  Elementary  and  Compound  Substances. 

— All  substances  are  classified  as  being  either  elementary 
or  compound.  Any  substance  that  can  not  be  sep- 
arated, by  any  Itnown  means,  into  tit'o  or  more 
essentially  different  kinds  of  matter,  is  called  an 


§  8  THE  DOMA1X   OF  CHEMISTRY.  3 

dement,  ^luy  substance  that  can  be  thus  separated 
is  called  a  compound.  Compounds  consist  of  two 
or  more  elements  in  chemical  combination.  The  atoms 
of  any  given  element  are  of  the  same  kind ;  those 
of  a  compound  are  of  two  or  more  kinds.  There  are  as 
many  kinds  of  atoms  as  there  are  elements.  Sixty-six 
elements  have  been  already  recognized  (see  Appendix  1). 
Some  of  these  are  very  abundant  and  widely  distributed ; 
others  have  been  found  only  in  such  minute  quantities 
that  even  their  properties  have  not  yet  been  satisfactorily 
determined.  Other  elements  will  doubtless  be  discovered 
and  it  is  possible  that  some  substances  now  considered  ele- 
mentary will  be  found  to  be  compound.  In  fact,  nearly 
every  improvement  in  our  methods  of  examination  (see 
Ph.,  §  638,  b)  leads  to  the  detection  of  elements  previously 
unknown.  Silver  and  gold  are  elements  ;  wood  and  water 
are  compounds. 

7.  Organic   and   Inorganic    Substances.  — 

Substances  that  have  been  formed  by  animal  or 
vegetable  life  are  called  organic  substances ;  those 
that  have  not  been  thus  formed  are  called  inor- 
ganic. Flesh  and  bone,  oak  and  cotton  are  organic  sub- 
stances; metals,  air,  water,  etc.,  are  inorganic. 

(a.)  This  distinction  is  less  important  than  formerly.  Of  late 
years,  chemists  have  succeeded  in  producing  several  "  organic  "  sub- 
stances from  "inorganic"  materials.  The  old  barrier  between  or- 
ganic and  inorganic  chemistry  is  being  broken  down,  and  many 
chemists  now  look  forward,  not  hopelessly,  to  a  future  when  even 
food  may  be  made  in  the  chemical  laboratory  as  well  as  in  the  fields 
and  pastures. 

8.  Forms  of  Attraction.— Each  of  the  three  di- 


4  THE  DOMAIN  OF  CHEMISTRY.  §  8 

visions  of  matter  has  its  peculiar  form  of  attraction.  The 
attractions  of  masses  and  molecules  pertain  more  particu- 
larly to  natural  philosophy ;  the  attraction  existing  be- 
tween atoms  pertains  chiefly  to  chemistry.  Atomic  at- 
traction is  called  chemism  or  cJiemical  affinity. 

Experiment  1. — Pulverize  separately  a  teaspoonful  each  of  loaf- 
sugar  and  potassium  chlorate  (chlorate  of  potash)  and  mix  them 
together  upon  a  porcelain  plate.  Dip  a  glass  rod  (Appendix  4,  a)  into 
strong  sulphuric  acid  and  hold  the  rod  in  a  horizontal  position  over 
the  mixture  and  close  to  it  but  so  as  not  to  touch  it.  Notice  that 
there  is  no  peculiar  action  visible.  Now  hold  the  rod  in  a  vertical 
position,  so  that  a  drop  of  acid  Vill  fall  upon  the  mixture.  The 
mixture  is  immediately  ignited. 

Experiment  2. — Into  a  mortar,  put  a  bit  of  potassium  chlorate  the 
size  of  a  grain  of  wheat,  and  cover  it  with  powdered  sulphur. 
Notice  that  there  is  no  peculiar  action  visible.  Now  rub  them  to- 
gether vigorously  with  the  pestle.  A  sharp  explosion  or  a  succes- 
sion of  minute  explosions  will  take  place. 

5^"  See  the  Caution  following  Experiment  36. 

Experiment  3. — Cover  a  bit  of  phosphorus,  the  size  of  a  pin  head, 
with  pulverized  potassium  chlorate  and  wrap  the  materials  in  a  bit 
of  soft  paper,  so  as  to  form  a  minute  torpedo.  The  phosphorus  and 
the  particles  of  potassium  chlorate  lie  close  together,  but  no  action 
takes  place.  Now  place  the  torpedo  on  a  small  anvil  or  other 
smooth,  hard  surface  and  force  the  phosphorus  and  potassium  chlorate 
closer  together  by  a  blow  with  a  hammer.  A  violent  explosion  takes 
place. 

9.  Peculiarities  of  Chemical  Affinity.— The 

foregoing  experiments  illustrate  the  fact  that  atomic  at- 
traction is  effective  at  insensible  distances  only. 
In  only  a  few  cases  is  it  possible  by  mechanical  means  to 
bring  solid  particles  sufficiently  near  each  other  for  the 
desired  chemical  action.  The  necessary  freedom,  of 
molecular  motion  (Ph.?  §§  54,  55,  57),  is  generally  secured 
by  solution,  fusion  or  vaporization  of  one  or  more  of  the 


§  10  THE  DOMAIN  OF  CHEMISTRY.  5 

materials  used.  Hence  solvents  and  heat  are  important 
agents  in  the  chemical  laboratory.  Another  peculiarity  is 
that  atomic  attraction  is  most  energetic  between 
dissimilar  substances. 

(«.)  A  body  is  dissolved  or  "  in  solution"  when  it  is  so  finely  di- 
vided and  its  particles  are  so  completely  dispersed  through,  the  water 
or  other  solvent  that  they  can  neither  be  seen  nor  ssparated  from 
the  liquid  by  filtering. 

1O.  Physical   and   Chemical    Changes.  —  A 

physical  change  is  one  that  docs  not  change  the 
composition  of  the  molecule,  and,  therefore,  does 
not  change  the  nature  of  the  substance  acted 
upon.  A  chemical  change  is  one  that  does  change 
the  composition  of  the  molecule  and,  therefore, 
does  change  the  nature  of  the  substance. 

(a.)  A  piece  of  marble  may  be  ground  to  powder,  but  each  grain 
is  marble  still.  Ice  may  change  to  water  and  water  to  steam,  yet  the 
nature  of  the  substance  is  unchanged.  Such  as  these  are  physical 
changes.  But  if  the  piece  of  marble  be  acted  upon  by  sulphuric 
acid,  a  brisk  effervescence  takes  place,  caused  by  the  escape  of  carbon 
dioxide,  which  was  a  constituent  of  the  marble ;  calcium  sulphate 
(gypsum),  not  marble,  will  remain.  (Experiment  185.)  The  water 
may,  by  the  action  of  electricity,  be  decomposed  into  hydrogen  and 
oxygen.  (Experiment  12.)  Such  as  these  are  chemical  changes. 

Experiment  4. — Rub  together  in  a  mortar  4  g.  of  sodium  sulphate 
crystals  and  2  g.  of  potassium  carbonate.  The  two  solids  form  a 
liquid.  Repeat  the  experiment  with  ice  and  salt. 

Experiment  5. — Saturate  4  cu.  cm.  of  water  with  calcium  chloride 
(§  291).  Add  slowly  0.5  cu.  cm.  of  sulphuric  acid.  The  two  trans- 
parent liquids  form  a  white,  opaque  solid.  [Ph.,  §  524  (4).] 

Experiment  G. — Moisten  the  inner  surface  of  a  beaker  glass,  or 
clear  tumbler,  with  strong  ammonia  water,  and  place  a  few  drops  of 
the  liquid  in  the  glass.  Cover  it  with  a  glass  plate  (or  piece  of 
writing  paper).  Moisten  the  inner  surface  of  a  similar  clear  glass 


6 


THE   1)OMAL\   OF   CHEMISTRY. 


id 


r\ 


vessel  with  hydrochloric  (muriatic)  acid.     Invert  the  second  vessel 
over  the  first,  mouth  to  mouth,  so  that  the  contents  of  the  two 

vessels  shall  be  sep- 
arated only  by  the 
glass  plate.  Each 
vessel  is  filled  with 
an  invisible  gas. 
Now  remove  the 
glass  plate.  The  in- 
visible gases  diffuse 
into  each  other  and 
form  a  dense  cloud 
that  slowly  settles 
in  the  form  of  a 

white  powder. 
riG.  i. 

Experiment  7. — Dissolve  five  or  six  lumps  of  loaf  sugar  in  a  beaker 
glass  or  a  tea-cup  with  as  little  warm  water  as  possible.  Place  the 
beaker  glass  upon  a  large  plate  and  into  the  syrup  slowly  pour  strong 
sulphuric  acid,  stirring  the  contents  of  the  beaker  glass  at  the  same 
time.  A  black,  porous  solid  will  fill  the  glass,  and  probably  overflow 
upon  the  plate. 

Experiment  8. — In  a  conical  test-glass,  or  a  test-tube,  dissolve  a  few 
crystals  (0.5  g.)  of  silver  nitrate  in  10  cu.  cm.  of  water.  In  a  second 
test-glass,  place  a  similar  solution  of  lead  nitrate  ;  in  a  third,  a  solu- 
tion of  mercuric  chloride  (corrosive  sublimate)  ;  in  a  fourth,  10  cu.  cm. 
of  chlorine  water  (Exp.  86),  to  which  a  few  drops  of  a  freshly  prepared 
dilute  solution  of  starch  have  been  added.  Each  solution  will  be  as 
clear  as  water.  To  each,  add  a  few  drops  of  the  colorless  solution  of 
potassium  iodide,  and  notice  the 
colors  produced,  yellow,  orange, 
scarlet  and  blue. 

Experiment  9. — Into  a  glass  tube 
2  cm.  in  diameter,  and  15  or  20  on . 
in  length,  having  one  end  closed 
and  rounded  like  a  test-tube,  place 
20  mg.  of  freshly  burnt  char- 
coal. Draw  the  upper  part  of  the 
tube  out  to  a  narrow  neck.  Fill  the 
tube  with  dry  oxygen  and  seal  the 
tube  by  fusing  the  neck.  Weigh 
the  tube  and  its  contents  very  care-  FIG.  2. 


§  II  THE  DOMAIN  OF  CHEMISTRY. 

fully.  By  gradually  heating  the  rounded  end  of  the  tube,  the  char- 
coal may  be  ignited  and,  with  sufficient  care,  entirely  burned  without 
breaking  the  tube.  When  the  charcoal  has  disappeared,  weigh  the 
tube  and  its  contents  again.  The  chemical  changes  that  led  to  tne 
disappearance  of  the  charcoal  have  caused  no  change  in  the  weight 
of  the  materials  used.  See  App.  4,  c  and  d. 

Experiment  10. — Put  a  few  small  pieces  of  zinc  jnto  a  test-tube 
and  pour  some  strong  nitric  acid  upon  them.  Reddish  fumes  appear, 
and  the  tube  becomes  warm. 

11.  Characteristics  of  Chemical    Action. — 

From  the  preceding  pages  we  learn  that  atomic  attraction  is 
a  very  powerful  agent  in  its  own  field,  but  that  it  acts  only 
upon  the  minutest  divisions  of  matter  (atoms)  and  at  dis- 
tances too  small  to  be  perceptible.  The  resulting  action 
leads  to  a  general  change  of  properties,  physical  and 
chemical,  always  excepting  weight.  This  exception  is 
the  direct  result  of  the  indestructibility  of  matter  (Ph., 
§  37).  Every  atom  of  matter  has  a  certain  definite  weight, 
and  as,  in  these  changes,  the  atoms  are  merely  rearranged 
but  none  destroyed  or  created,  the  sum  total  of  the  weights 
of  these  atoms  must  remain  unchanged.  Whenever  these 
atoms  rush  together  (synthesis,  §  18)  they  develop  heat, 
which  is  thus  a  frequent  result  of  chemical  action  (Ph., 
§  568).  As  will  be  seen  from  the  next  paragraph,  chemi- 
cal action  takes  place  between  definite  quantities  of  mat- 
ter only. 

Experiment  11. — Fine  iron  filings  and  powdered  sulphur  may  be 
mixed  in  any  proportion.  From  such  a  mixture  the  iron  may  be  re- 
moved by  a  magnet ;  the  sulphur  may  be  removed  by  solution  in 
carbon  disulphide  (§  201),  nitration  and  subsequent  evaporation 
of  the  nitrate.  The  iron  is  still  iron,  the  sulphur  is  still  sulphur. 
In  the  mixture  the  free  iron  or  sulphur  particles  may  be  detected 
with  a  microscope.  Now  mix  thoroughly  4  g.  of  the  powdered  sul- 
phur with  7  g.  of  the  iron  filings,  and  place  the  mixture  in  an  igni- 
tion tube  (Appendix  4,  a)  about  12  cm.  long.  By  wooden  nippers, 


8  THE   DOMAIN  OF   CHEMISTRY.  §12 

hold  the  tube  over  the  gas  or  alcohol  lamp  (Appendix  15),  as  shown 
in  the  figure.  The  sulphur  melts  and  combines  with  the  iron  to 
form  ferrous  sulphide  (sulphide  or  sul- 
phuret  of  iron).  There  is  no  longer  any 
thing  to  be  attracted  by  a  magnet,  or  to  be 
dissolved  by  carbon  disulphide.  The  mi- 
croscope reveals  no  particle  of  either  con- 
stituent of  the  mixture.  The  ferrous  sul- 
phide, which  contains  the  iron  and  the  sul- 
phur, differs  from  both  in  appearance  and 
properties.  It  always  consists  of  7  parts  of 
iron  to  4  parts  of  sulphur  by  weight  (or  56  : 
32),  however  or  wherever  obtained.  Instead 
of  using  the  ignition-tube  represented  in 
Fig.  3,  the  mixed  iron  and  sulphur  may  be 
placed  in  a  small  Hessian  crucible  (Appen- 
dix 21),  covered  with  a  similar  inverted 
pIG  crucible  and  heated  in  a  coal  fire. 

12.  Mixtures  and  Compounds.  —  Mixtures  of 
two  or  more  substances  may  be  formed  by  mingling  them 
in  all  conceivable  proportions,  but  a  compound  formed  by 
chemical  action  consists  of  certain  invariable  proportions 
of  its  constituents.  Thus,  oxygen  and  hydrogen  may  be 
mixed  in  any  desired  proportion,  but  they  will  unite  to 
form  water  only  in  the  ratio  of  eight  parts  to  one  by 
weight,  or  one  part  to  two  by  volume.  When  iron  rusts,  the 
oxygen  of  the  air  combines  with  the  metal  at  the  rate  of 
3  grams  or  ounces  of  oxygen  to  7  grains  or  ounces  of  iron. 
No  chemist  can  make  3  grams  of  oxygen  unite  with  G 
grams  of  iron.  In  a  mixture,  the  constituents  are 
said  to  be  free ;  in  a  compound,  they  are  said  to  be 
combined  or  in  combination. 

(a.)  Gunpowder  is  composed  of  charcoal,  sulphur  and  potassium 
nitrate  (nitre  or  saltpeter)  mechanically  mixed.  The  potassium  nitrate 
may  be  washed  out  by  water  and,  by  evaporating  the  water,  may  be 
secured  in  the  solid  form.  The  sulphur  may  then  be  removed  from 


§  13  THE  DOMAIN  OF  CHEMISTRY.  9 

the  mixture,  as  in  Experiment  11.  The  charcoal  will  be  left  alone. 
The  constituents  of  gunpowder  could  not  be  thus  separated  if  they 
were  in  chemical  union.  When  gunpowder  is  ignited,  the  constit- 
uents combine  to  form  enormous  volumes  of  gaseous  products. 

13.  Chemistry  Defined.  —  Chemistry  is  the 
branch  of  science  that  examines  the  elements  and 
their  compounds  experimentally,  and  investigates 
the  laws  that  regulate  their  combination. 

(a.)  The  experimental  examination  above  mentioned  has  to  do  with 
the  properties  and  composition  of  substances  and  the  known  or  pos- 
sible chemical  changes  they  may  undergo. 

(6.)  Such  changes  as  we  have  seen  in  the  foregoing  experiments 
can  not  be  foretold  ;  they  can  be  ascertained  only  by  experiment ; 
i.  e.,  by  placing  the  substances  in  question  under  circumstances  that 
the  chemist  can  control  and  vary.  Hence,  chemistry  is  called  an 
experimental  science. 


WATER    AND    ITS    CONSTITUENTS. 


i. 


ANALYSI  S    OF    WATER. 

14.  The  First  Question.  —  One  of  the  most  famil- 
iar substances  in  nature  is  water.  Its  appearance,  uses, 
occurrence,  and  many  of  its  valuable  properties  are  mat- 
ters ^of  common  observation  and  every  day  application. 
We  know  that  it  furnishes  the  units  of  weight  (Ph.,  §  36), 
of  specific  gravity  (Ph.,  §  242),  and  of  specific  heat  (Ph., 
§  532).  We  know  that  it  may  assume  the  solid,  liquid  and 
gaseous  forms  in  succession.  While  these  and  many  others 
are  well-known  facts,  the  healthy  mind  still  asks,  "  Of  what 
is  it  made  ?  "  This  very  question,  "  Of  what  is  it  made  ?  " 
which  thus  confronts  the  young  chemist  at  the  threshold 
of  the  science,  will  force  itself  upon  his  attention  at  every 
step  of  his  progress.  It,  therefore,  deserves  careful  con- 
sideration. Working  together,  we  shall  find  an  answer. 

Experiment  12.  —  The  apparatus  represented  in  Fig.  4  consists  of 
a  vessel  containing  water  (to  which  a  little  acid  has  been  added  to 
increase  its  conductivity)  in  which  are  immersed  t\vo  platinum 
strips  which  constitute  the  two  electrodes  of  a  galvanic  battery. 
Glass  tubes  containing  acidulated  water  are  inverted  over  the  plati- 
num electrodes.  A  battery  of  three  or  four  Grove  cells  will 
answer  very  well  for  our  present  purpose  (Ph..  §  384).  When  the 


WATER. 


11 


FIG.  4. 

circuit  is  closed  and  the  current  passed  through  the  water  between 
the  electrodes,  bubbles  will  be  noticed  rising  in  the  glass  tubes  and 
gradually  displacing  the  water  therefrom.  Gas  will  accumulate 
about  twice  as  rapidly  in  the  tube  covering  the  negative  electrode 
(Ph.,  §  377)  as  in  the  other. 

15.  Another  Question.— By  the  time  the  water 
has  been  displaced  from  one  of  the  tubes,  we  shall,  per- 
haps, be  wondering  what  is  in  the  tube.  This  question, 
"  IVTiat  is  it  ?  "  is  also  continually  recurring  to  the  chemist. 
Lift  the  tube  carefully,  holding  it  mouth  downward,  and 
gently  cover  its  mouth  with  the  thumb.  It  looks  like  air ; 
is  it  air  ?  To  obtain  our  answer, 
we  must,  as  usual,  try  an  experi- 
ment. 


Experiment  13. — Light  a  taper  or  dry 
splinter  of  wood,  and  thrust  it  into  the 
tube,  as  shown  in  Fig.  5.  The  taper 
flame  will  be  extinguished  and  the  gas 
will  burn  at  the  mouth  of  the  tube. 
Notice  the  appearance  of  the  flame. 
The  taper  may  be  withdrawn  and  re- 
lighted at  the  mouth  of  the  tube  and 
the  experiment  repeated.  Was  it  avr  in 
the  tube  ? 


FIG.  5. 


12  WATER.  §  15 

We  have  now  interrogated  Nature,  conversing  with  her 
in  her  own  language.  The  question  being  properly  put, 
she  answered  that  it  was  not.  air.  The  answer  was  intelli- 
gible and  satisfactory.  As  a  matter  of  present  convenience, 
we  shall  call  this  gas  hydrogen. 

16.  What   is  in  the   other   Tuhe?— By  this 
time  the  other  tube  is  probably  full  of  gas,  generated  at 
the  positive  electrode.     If  so,    break  the  circuit    (Ph., 
§  376)  and  remove  the  tube,  closing  its  mouth  as  before. 
Is  it  air  ?    Is  it  hydrogen  ? 

Experiment  14- — To  put  these  questions  in  proper  form,  light  the 
taper  and  let  it  burn  until  a  spark  will  remain  upon  the  wick  when 
the  flame  is  blown  out.  Thrust  the  glowing  taper  (or  a  glowing 
splinter)  into  the  tube.  The  taper  is  rekindled  and  burns  with  un- 
usual vigor  and  brilliancy. 

The  answer  is  as  prompt  and  unmistakable  as  before. 
It  was  not  air;  it  was  not  hydrogen.  For  purposes  of 
present  convenience,  we  shall  call  this  gas  oxygen. 

17.  The  Synthesis  of  Water.— So  far,  we  have 
seen  that  water  is  composed  of  oxygen  and  hydrogen, 
there  being  twice  as  great  a  volume  of  the  latter  as  of  the 
former.     We  have  also  learned  that  these  gases  look  like 
common  air,  but  that,  in  their  action  upon  burning  sub- 
stances, they  are  very  different  from  air  and  from  each 
other.    If  we  wish  to  know  whether  water  has  any  other 
constituent,  or  suspect  that  these  gasos  came  from  the 
small  quantity  of  acid  used  to  increase  the  water's  con- 
ductivity for  the  electric  current,  it  would  be  natural  to 
try  to  unite  these  gases  and  see  what  the  product  is.     For 
such  an  experiment  we  are  not  quite  ready.     By  the  anal- 
ysis of  something  we  have  secured  separated  oxygen  and 


§  18  WATER.  13 

hydrogen  ;  for  their  synthesis,  it  is  desirable  that  we  know 
more  about  them  (Exps.  28  and  53). 

18.  Analysis,  Synthesis,  and  Metathesis.— 

By  chemical  analysis,  we  mean  the  breaking  up  of  a  com- 
pound into  its  constituent  parts  (Exp.  12) ;  by  chemical 
synthesis,  we  mean  the  union  of  two  or  more  substances  to 
form,  one,  different  from  any  of  its  constituents  (Exp.  27). 
Synthesis  is  chiefly  used  to  prove  the  results  of  analysis. 
Metathesis  consists  in  the  interchange  of  dissimilar  atoms 
or  groups  of  atoms  between  two  sets  of  molecules,  and 
implies  that  the  structure  of  these  molecules  is  not  other- 
wise altered  (§  74  a).  It  may  almost  be  regarded  as  a  con- 
currence of  analysis  and  synthesis. 


14 


HYDROGKN. 


§19 


HYDROGEN. 

Symbol,  H  ;  specific  gravity,  1 ;  atomic,  weight,  1  m.  c.  (§  62) ; 
molecular  weight,  2  m.  c. ;  quantivalence,  1  (§  92). 

19.  Occurrence. — It  was  long  thought  that  hydro- 
gen did  not  occur  free  in  nature,  but  it  has  been  found 
uncombined  in  meteors,  volcanic  gases,  and  the  solar  and 
stellar  atmospheres.  In  combination,  it  is  almost  every- 
where, being  found  in  water,  in  petroleum,  and  in  all 
animal  and  vegetable  substances. 

Note.  —  The  word  hydrogen  is  derived  from  the  Greek  hudor 
(=  water)  and  gennao  (—  I  produce). 


FIG.  6. 

2O.  The  Apparatus. — Provide  a  good  bottle,  about 
20  cm.  (8  in.)  high,  and  having  a  mouth  about  2.5  cm. 
(lin.)  in  diameter.  See  that  the  edges  of  the  bottle  are 
smooth,  so  that  they  will  not  cut  the  cork.  Get  a  caout- 
chouc stopper  or  fine  grained  cork  (App.  9)  that  will  fit 


§  21  HYDROGEN.  15 

the  mouth  of  the  bottle  snugly,  and  furnish  it  with  a 
funnel  tube,  a,  and  a  delivery  tube,  b,  (App.  4,  b)  as  shown 
in  Fig.  6.  The  funnel  tube  should  be  of  such  a  length 
that,  when  the  cork  is  in  its  place,  the  tube  will  reach 
within  1  cm.  (£  in.)  of  the  bottom  of  the  bottle.  To 
the  delivery  tube,  b,  connect  a  piece  of  glass  tubing,  d, 
bent  near  each  end.  The  connection  may  be  made  by  a 
short  piece  of  snugly  fitting  rubber  tubing,  c.  If  desira- 
ble, c  and  d  may  be  replaced  by  a  piece  of  rubber  tubing 
of  suitable  length.  The  lower  end  of  d  terminates  beneath 
the  inverted  saucer  or  tin  plate,  e,  placed  in  the  pan,/. 
The  saucer  has  a  notch  in  its  edge  for  the  admission  of  d, 
and  a  hole  in  the  middle  of  its  bottom  ;  this  hole  should  be 
a  little  larger  than  the  delivery  tube.  Into  the  pan,  pour 
enough  water  to  cover  the  saucer.  Fill  a  bottle,  g,  with 
water  and  invert  it  over  the  hole  in  the  bottom  of  e. 
Atmospheric  pressure  will  keep  the  water  in  g.  (Ph., 


21.  The  Preparation.—  Granulate  some  zinc  by 
melting  about  250  #.  (-J-  lb.)  in  a  Hessian  crucible  or  iron 
ladle,  and  slowly  pouring  it,  while  very  hot,  into  a  pail  or 
tab  of  water,  from  as  great  a  height  as  you  can  conven- 
iently reach.  Put  about  25  g.  (1  oz.)  of  this  granulated 
zinc  (clippings  of  ordinary  sheet  zinc  will  answer,  but  not 
so  well)  into  the  gas  bottle,  B,  pour  in  water  until  the 
bottle  is  about  a  quarter  full  and  replace  the  cork.  Be  sure 
that  all  of  the  joints  about  the  mouth  of  the  bottle  are  tight. 
To  test  this,  place  the  delivery  tube  between  the  lips  and 
force  air  into  the  bottle  until  water  rises  in  the  funnel  tube 
and  nearly  fills  the  funnel.  Place  the  end  of  the  tongue 
against  the  end  of  the  delivery  tube  to  prevent  the  escape 


16  HYDROGEN.  §  21 

of  air  from  the  bottle.  If  the  water  retains  its  elevation 
in  a,  the  joints  are  tight.  If  the  water  falls  in  a  to  the 
level  of  that  in  B,  the  apparatus  leaks  and  must  be  put 
into  satisfactory  condition  before  going  on.  Pour  sulphuric 
or  hydrochloric  acid  through  the  funnel  tube,  a,  in  small 
quantities,  not  more  than  a  thimble  full  at  a  time.  Gas 
will  be  generated  with  lively  effervescence  in  B  and  bubble 
up  in  g,  displacing  the  water  therefrom.  This  method  of 
collecting  a  gas,  by  the  displacement  of  water,  is  called 
"  collecting  over  water."  It  will  be  thus  briefly  indicated 
hereafter. 

22.  The  Collection.— The  gas  first  delivered  will 
be  mixed  with  the  air  that  was  in  the  apparatus  at  the 
beginning  of  the  experiment.  This  should  be  thrown 
away,  as  it  is  dangerously  explosive.  When  a  quantity  of 
gas  about  equal  to  the  contents  of  the  gas  bottle  has  thus 
been  allowed  to  escape,  fill  a  test  tube  or  small  wide- 
mouthed  bottle  with  the  gas,  remove  it  from  the  water  pan, 
being  careful  to  hold  it  mouth  downward,  and  bring  a 
lighted  match,  or  other  flame,  to  the  mouth.  If  the  gas 
burns  with  a  puff,  or  slight  explosion,  it  is  not  yet  free 
from  air.  In  this  way  continue  to  test  the  gas,  as  it  is  de- 
livered, until  it  burns  quietly  at  the  mouth  of  the  tube 
and  within  it.  Keep  the  end  of  the  delivery  tube,  d,  under 
water  until  you  are  sure  that  the  hydrogen  is  unmixed 
with  air.  Do  not,  at  any  time,'  bring  a  flame  into  contact 
with  any  considerable  quantity  of  hydrogen  until  you  have 
established  its  non-explosive  character  by  testing  a  small 
quantity  as  just  described.  For  such  tests,  bottles  are 
not  so  good  as  test  tubes  or  cylinders  (App.  7),  as  they 
confine  the  gas  more  and  thus  increase  the  danger  in  case 


§  23  HYDROGEN.  17 

of  an  explosion.  Add  acid  through  the  funnel  tube  from 
time  to  time,  as  may  be  necessary  to  keep  up  a  brisk  effer- 
vescence in  the  gas  bottle.  Fill  several  bottles  with  the 
unmixed  gas,  slipping  the  mouth  of  each,  as  it  is  filled, 
into  a  saucer  containing  enough  water  to  seal  the  mouth 
of  the  bottle  and  prevent  the  escape  of  the  hydrogen.  If 
you  have  used  the  pneumatic  trough  (App.  12)  instead  of 
the  water  pan,  the  bottles  may  be  left  upon  the  shelf  of 
the  trough,  which  should  be  a  little  below  the  surface  of 
the  water.  At  your  earliest  convenience,  fill  one  of  the 
gas  holders  (App.  13)  with  hydrogen. 

Note. — There  are  several  other  ways  of  preparing  hydrogen. 
Some  of  them  will  be  cfoisidered  subsequently. 

23.  The  Reaction.— The  hydrogen  just  prepared 
resulted  from  the  action  of  the  zinc  upon  the  acid,  water 
being  used  to  dissolve  the  solid  compound  thus  formed. 
Resulting  from  this  action  we  have  the  hydrogen  gas  and 
a  chemical  compound  called  zinc  chloride  if  hydrochloric 
acid  was  used,  or  zinc  sulphate  if  sulphuric  acid  was  used. 
This  compound  remains  dissolved  in  the  water  of  the  gas 
bottle.  The  zinc  chloride  or  sulphate  may  be  obtained 
separate  by  filtering  and  evaporating  the  solution.  We 
may  represent  hydrogen  by  the  symbol  H,  and  zinc  by  the 
symbol  Zn.  Hydrochloric  acid  is  composed  of  hydrogen 
and  chlorine  (an  element  which  we  shall  soon  study  §  104) 
and  maybe  represented  by  HCI.  The  zinc  chloride  is 
composed  of  zinc  and  chlorine  and  may  be  represented  by 
ZnClj,.  In  fact,  chemists  of  all  nations  represent  these 
substances  by  these  convenient  abbreviations  and  other 
substances  by  similar  symbols,  as  will  be  explained  soon 
(§  56).  The  chemical  changes  that  took  place  in  the  gas 


18 


HYDRO  O  EN. 


bottle  may  be    represented    by   the   following    equation 

(§127): 

Zn  +2HCI=:ZnCI2  -f  H2. 

The  free  zinc  united  with  the  chlorine  of  the  acid  to 
form  the  zinc  chloride,  thus  setting  free  the  hydrogen  of 
the  acid.  As  hydrogen  is  a  gas,  it  bubbled  through  the 
water  causing  the  effervescence.  As  zinc  chloride  is  a 
soluble  solid,  it  was  dissolved  by  the  water.  From  the 
clashing  together  of  atoms  in  this  reaction,  much  heat  was 
developed  (Ph..  §§  674,  676).  At  the  close  of  the  experi- 
ment, small  black  particles  are  sometimes  to  be  seen  float- 
ing in  the  solution  in  the  gas  bottle.  These  are  bits  of 
carbon  that  were  present,  as  impurities,  in  the  zinc. 

Experiment  15. — Instead  of  "collecting  over 
water,"  collect  the  gas  by  "  upward  displacement," 
as  follows  :  Bring  the  delivery  tuhe,  d,  of  the  gas 
bottle  (Fig.  6)  or  gas  holder  into  a  vertical  position. 
Hold  over  it  a  test  tube,  or  small  bottle,  as  shown  in 
Fig.  7,  and  cause  the  H  to  flow  rapidly  through  the 
tube,  d.  In  a  few  moments  the  air  will  be  driven 
from  the  test  tube  and  replaced  with  H.  That  this 
gas  is  not  mixed  with  air  (after  allowing  the  H  to 
flow  a  sufficient  length  of  time)  may  be  shown  by 
testing  it  in  the  manner  described  in  §  22.  What 

does  this  experiment  teach  ? 
Experiment  16. — Refill  the  bottle  with  H,  cover  the  mouth,  turn 

the  bottle  right  side  up,  remove  the  cover  and  quickly  apply  a  flame. 

How  does  the  H  flame  differ  from  those  previously  seen  ?    Why  ? 
Experiment  17. — Take  two  cylinders  or 

large  test  tubes  of  equal  size.    Fill  one  of 

them,  a,  with  H.    Bring  the  mouth  of  a 

to  that  of  b,  gradually  turn  a  from  its 

inverted  position,   as    shown  in   Fig.   8, 

until  it  is  upright  below  b.     Place  a  upon 

a  table  and  in  half  a  minute  test  the  two 

tubes  with  a  flame.     If  the  experiment 

has  been  neatly  performed,   it  will  be  FIG.  8. 

found  that  b,  which  had  air,  now  has  H, 


FIG.  7. 


19 


and  that  a,  which  had  H,  now  has  air.  The  K  was  poured  upward 
from  a  to  &.  This  is  called  "  upward  decantation,"  and  is  possible 
because  of  the  extreme  levity  of  this  gas  as  compared  with  the  sur- 
rounding air. 

Experiment  IS. — Equipoiss  two  beaker  glasses,  as  shown  in  Fig.  9, 
Fill  the  inverted  beaker  with  H,  by  upward  deca-ntation.  The  equi- 
librium will  be  destroyed,  and  the  glass  containing  H  will  rise. 


FIG.  Q. 

Experiment  19. — To  the  flexible  rubber  delivery  tube  of  a  gas 
holder  containing  H,  attach  the  stem  of  an  ordinary  clay  pipe,  or  a 
small  glass  funnel.  With  the  gas  flowing  slowly  (the  flow  being 
controlled  by  the  stop-cock),  dip  the  pipe  into  a  saucer  of  soap  suds, 
and,  when  a  film  is  formed  over  the  mouth  of  the  pipe,  turn  its 
mouth  upward  and  open  the  stop-cock  wider.  The  bubble  soon 
breaks  away  from  the  pipe  and  rises  like  a  balloon. 

Note. — The  last  experiment  will  be  more  satisfactory  if  the  soap 
solution  be  prepared  by  making  a  strong  solution  of  white  castile 
soap  in  warm  soft  water  that  has  been  recently  boiled,  and  adding 
half  its  volume  of  glycerin.  Shake  the  mixture  thoroughly,  and  it 
is  ready  for  use. 

Experiment  20.  —  Over  a  vertical    tube  delivering    H,    hold    a 


HYDROGEN. 


' 


sheet  of  gold  leaf  or  unglazed  paper.  The  gas  will  pass  through 
the  gold  or  paper,  and  may  be  lighted  on  the  upper  side  of  the 
sheet. 

Experiment  21.  —  The  remarkably 
rapid  diffusion  of  H  may  be  shown  as 
follows:  Cement  with  sealing-wax 
the  porous  cup  of  a  Grove  cell  to  a 
glass  funnel,  mouth  to  mouth.  Pro- 
long the  stem  of  the  funnel,  s,  with 
a  glass  tube  passing  snugly  through 
the  cork  of  the  bottle  B.  The  funnel 
may  be  supported  by  the  retort  stand, 
R,  and  connected  to  the  glass  tube  by  a 
piece  of  rubber  tubing.  The  bottle  is 
to  be  half  full  of  water  and  provided 
with  a  delivery  tubs,  d,  drawn  out  to  a 
jet  above  and  dipping  into  the  water 
below.  When  a  bell  glass,  G,  contain- 
ing H  is  placed  over  the  porous  cell, 
the  H  diffuses  inward  so  much  more 
rapidly  than  the  air  can  diffuse  out- 
ward that  an  increased  pressure  is 
exerted  on  the  surface  of  the  water  in 
B.  If  all  of  the  joints  are  tight,  water 
will  be  thrown  from  the  jet,  as  shown 
in  Fig.  10.  The  experiment  may  be 
simplified  by  allowing  the  tube,  s,  to 
dip  into  water  in  an  open  vessel.  Bub- 
bles will  rise  through  the  water. 


FIG.  10. 


Experiment  22. — The  diffusion  of  H  may  be  shown  more  easily 
but  less  prettily  by  closing  one  end  of  a  glass  tube  3  or  4  cm. 
(H  in.)  in  diameter  and  about  30  cm.  (12  in.)  long,  with  a  plug  of 
plaster  of  Paris  1  or  2  cm.  thick,  filling  it  with  H  by  upward 
displacement  and  placing  the  mouth  of  the  tube  in  a  tumbler  of 
water.  The  outward  diffusion  of  the  gas  through  the  porous  septum 
reduces  the  pressure  on  the  water  in  the  tube,  which  is  then  forced 
upward  by  atmospheric  pressure.  An  argand  lamp  chimney  answers 
well  for  the  experiment.  The  plug  may  be  inserted  by  spreading  a 
stiff  paste  of  the  plaster  and  water  in  a  layer  of  the  desired  thickness 
upon  a  piece  of  writing-paper  and  pressing  one  end  of  the  chimney 
down  into  it.  In  an  hour  or  two  the  plaster  will  have  set.  The  paper 
may  then  be  easily  removed  and  the  plaster  outside  the  tube  broken 
off.  Allow  it  to  dry  over  night  before  using.  In  filling  the  tube 


§24 


HYDROGEN. 


with  gas,  hold  it  so  that  the  septum  will  be  covered  with  the  fleshy 
part  of  the  hand  to  prevent  premature  diffusion.  The  water  may  be 
colored  with  cochineal  or  indigo  or  ink. 

Experiment  23. — To  show  the  effect  of 
H  upon  sounds  produced  in  it,  fill  a  large 
bell  glass  with  the  gas,  suspend  it  mouth 
downward,  and  strike  a  bell  in  it,  as  shown 
in  Fig.  11.  Instead  of  the  bell,  one  of  the 
small  squeaking  toys  well-known  to  chil- 
dren may  be  sounded  in  the  H.  When 
the  gas  has  been  purified  (§  26),  the  pupil 
,$nay  with  safety  inhale  it  once  or  twice  and 
try  to  speak  or  to  sing  bass  with  his  lungs 
filled  with  it  (Ph.,  §  424). 

24.  Physical  Properties. — 

Hydrogen  is  a  transparent,   color-  .^j 
less,  tasteless,  odorless  gas,  as  may 
be  seen  by  direct  inspection.    It  is 
the  lightest  known  substance.    One 

liter  of  it  weighs  0.0896  grams,  which  weight  is  called 
a  crith ;  100  cu.  in.  weighs  2.14  grains.  It  refracts 
light  much  more  powerfully  than  air  (Ph.,  §  612),  and  is 
often  taken  as  the  standard  of  specific  gravity  for  aeriform 
bodies.  It  has  recently  been  liquefied  by  subjecting  it  to 
a  very  great  pressure  (Ph.,  §§  58,  59,  277),  at  a  very  low 
temperature.  Because  of  its  extreme  lightness,  it  diffuses 
more  rapidly  than  any  other  known  substance,  and  has  a 
peculiar  effect  upon  sounds  produced  in  it  (Ph.,  §  426). 
It  is  only  sparingly  soluble  in  water,  100  volumes  of  the 
liquid  absorbing  only  one  or  two  of  the  gas. 

(a.)  H  is  about  14|  times  as  light  as  air,  11,000  times  as  light  as 
water,  150,000  times  as  light  as  mercury,  and  240,000  times  as  light 
as  platinum. 

(6.)  That  H  is  not  very  soluble  in  water  is  shown  by  the  fact  that 
it  may  be  collected  over  water.  But  the  metal  palladium  absorbs  or 
"occludes"  several  hundred  times  its  volume  of  H.  forming  what 


HYDRO G EX. 


seems  to  be  a  true  alloy.     For  this  and  other  reasons  it  is  thought  by 
some  that  H  is  the  vapor  of  a  highly  volatile  metal. 

(c.)  We  have  many  metallic  solids  and  one  metallic  liquid  (§  334) 
which  may  be  solidified  by  cold.  Why  may  we  not,  it  is  asked,  have 
a  metallic  gas?  H  has  been  liquefied  ;  it  may  be  solidified.  In  fact, 
it  is  claimed  that  H  has  been  solidified. 

Mercury  vapor  is  present  in  the  "  vacuum  "  of  every  thermometer 
and  barometer.  As  we  know  a  metal  that  is  liquid  under  ordinary 
circumstances  and  solid  or  gaseous  under  peculiar  conditions,  it  is  not 
difficult  to  conceive  a  metal  that  is  gaseous  under  ordinary  circum- 
stances and  liquid  or  solid  under  peculiar  conditions.  The  metallic 
nature  of  H  has  not  yet  been  generally  admitted. 

(d.)  Palladium,  at  a  red  heat,  occludes  935  times  its  volume  of  H 
and  376  times  its  volume  at  the  ordinary  temperature.  After  absorb- 
ing the  gas,  the  tenacity,  specific  gravity,  thermal  and  electric  con- 
ductivity of  the  metal  are  diminished.  Platinum,  at  a  red  heat, 
absorbs  3.8  times  its  volume  of  H. 

.Experiment  24. — Repeat  Exp.  13,  and  describe  the  phenomena 
fully.  What  two  chemical  properties  of  H  does  this  experiment 
illustrate  ? 

Experiment  25. — Repeat  Exp.  19,  and  while  the  bubble  is  in  the 
air,  touch  it  quickly  with  a  lighted  taper.  Be  sure 
to  see  all  that  the  experiment  shows,  and  then  tell 
what  you  see. 

Experiment  26. — Replace  the  bent  delivery  tube 
of  the  gas  bottle  with  a  straight 
one  having  the  upper  part 
drawn  out  to  form  a  jet.  After 
the  H  has  been  escaping  for 
some  time,  test  small  quanti- 
ties of  it  until  you  are  sure  that 
it  is  unmixed  with  air.  Then, 
and  not  until  then,  apply  flame 
to  the  jet.  This  is  the  "  Philoso- 
pher's candle."  Hold  a  small 
coil  of  fine  wire  in  the  upper 
part  of  the  flame.  Describe 
fully  the  flame  of  the  "  Philoso- 
pher's candle  "  (Fig.  13). 

Experiment  27. — Over  the  flame  of  the  "  Philosopher's  candle," 
hold  a  clear,  dry,  cold  tumbler.  In  a  few  moments  the  clear  glass 


FIG.  12. 


FIG.  13. 


FIG.  14. 


§  24  HYDROGEX.  23 

will  become  dimmed  with  a  sort  of  dew,  evidently  caused  by  the 
condensation  of  some  vapor  formed  by  the  burning  of  H  in  air. 

Experiment  28.  —  Pass  a 
stream  of  H  from  the  gas 
'  holder  through  a  U-tube,  a, 
(Fig.  14),  containing  calcium 
chloride,  which  will  retain 
any  aqueous  vapor  that  may 
be  mixed  with  the  gas.  To 
the  further  end  of  this  dry- 
ing tube  attach  a  piece  of 
glass  tubing,  &,  drawn  out 
to  form  a  jet.  Over  the  jet, 
place  the  bulb  of  a  thistle  or 
funnel-tube,  c,  which  is  bent  and  connected  by  a  perforated  cork 
to  one  leg  of  the  U-tube,  d.  In  the  other  leg  of  this  U-tube,  place  a 
loosely  fitting  test  tube,  e,  nearly  filled  with  ice- water.  The  hydrogen 
flame  should  be  13  or  14  mm.  (|  in.)  long.  The  size  of  the  flame 
may  be  largely  controlled  by  regulating  the  pressure  at  the  gas  holder. 
In  four  or  five  minutes,  an  appreciable  quantity  of  liquid  will  be 
found  in  the  bend  of  d  ;  by  keeping  the  flame  steadily  burning  for 
half  an  hour,  a  considerable  quantity  of  the  liquid  will  be  secured. 
This  liquid  is  water.  Why  was  the  gas  passed  through  the  drying 
tube?  Why  was  the  test  tube  of  cold  water  placed  in  the  leg  of  d  ? 

Note. — The  leg  of  d  that  contains  e  would  better  be  connected 
by  rubber  tubing  with  an  aspirator  (App.  13),  and  the  flow  of  steam 
and  air  through  c  and  d  thus  increased. 

Experiment  29. — Over  the  flame  of  the  "  Philosopher's  candle," 
hold  a  glass  tube,  t,  30  or  40  cm.  (12  or  15  in.)  long,  as  shown  in 
Fig.  15.  By  moving  the  tube  up  and  down,  a  position  will  be 
found  in  which  the  apparatus  gives  forth  a  musical  tone.  If  the 
experiment  does  not  work  at  first,  vary  the  size  of  the  flame  or 
change  the  tube,  t,  for  a  larger  or  smaller  one.  The  current  of 
air  drawn  upward  into  t  (Ph.,  §  541)  gives  rise  to  a  series  of  minute 
explosions  which  follow  in  such  rapid  succession  that  a  continuous 
sound  is  produced  (Ph.,  §§  429,  469,  a.).  See  Fig.  15. 

Note.  —  The  two-necked  bottle,  w,  shown  in  Fig.  15  (p.  24),  is 
called  a  Woulffe  bottle.  Such  bottles  are  also  made  with  three 
necks.  As  the  mouths  are  smaller  than  that  of  the  gas  bottle  pre- 
viously described,  tight  joints  are  more  easily  secured,  Woulffe  bot- 
tles are  very  convenient  for  many  purposes.  See  App.  6. 


HYDROGEN. 


FIG.  15. 


Experiment  30. — If  you  Lave  a  piece  of  platinum  sponge,  the  size 
of  a  pea,  make  for  it  a  support  by 
winding  a  fine  wire  spirally  into  the 
form  of  a  little  cup.  Heat  the  sponge 
to  redness  in  the  lamp,  and  when  cold, 
hold  it  2  or  3  cm.  above  a  small  jet  of 
dry  H.  The  cold  gas  soon  heats  the 
cold  sponge  to  redness  ;  the  sponge  in 
turn  ignites  the  gas.  In  repeating  the 
experiment,  the  preliminary  heating  of 
the  sponge,  probably,  will  not  be  neces- 
sary. (§  398,  &.) 

Note.— The  heating  of  the  sponge 
drives  off  traces  of  certain  absorbable 
gases,  such  as  ammonia,  which  inter- 
fere with  the  inflaming  power  of  the 
platinum.  This  property  of  platinum 
bas  been  explained  by  saying  that  the 
metal  condenses  or  even  liquefies  a  film 
of  H  and  one  of  oxygen  on  its  surface,  and  that  the  two  condensed 
elements  when  brought  together,  under  circumstances  of  such  inti- 
mate contact,  chemically  unite  at  the  ordinary  temperature,  the  heat 
of  such  union  exciting  the  combination  of  the  rest  of  the  gases. 

25.  Chemical  Properties. — Hydrogen  is  an  ele- 
ment, combustible  at  about  500°  C.  (App.  3),  i.  e.,  it 
combines  chemically  with  the  oxygen  of  the  air  at  that 
temperature.  Its  flame  is  pale  (almost  non-luminous 
under  ordinary  atmospheric  pressure)  but  intensely  hot. 
The  burning  of  a  given  weight  of  it,  as  1  g.,  yields  more 
than  34,000  heat  units  (Ph.,  §  569),  it  having  thus  the 
greatest  heating  power  of  any  known  substance.  "When- 
ever burned,  either  in  the  free  state  or  in  combination 
with  other  elements  (e.  g.,  alcohol  or  petroleum),  the  pro- 
duct of  its  combustion  is  water.  It  does  not  support  ordi- 
nary combustion  or  respiration.  When  immersed  in  it,  a 
lighted  taper  is  extinguished  and  an  animal  is  suffocated, 
in  both  cases  because  of  the  absence  of  oxygen.  It  forms 


§  25  HYDROGEN.  25 

an  explosive  mixture  with  air  or  oxygen.  It  is  the 
standard  of  atomic  weight  (§  64)  and  of  quantivalence 
(§93). 

Experiment  31. — Pass  the  delivery  tube  from  the  gas  holder  to  the 
bottom  of  a  drying  bottle,  a,  nearly  filled  with  pieces  of  pumice- 
stone  saturated  with  concentrated  sulphuric  acid.  As  the  gas  rises 
through  the  drying  bottle  it  comes  into  contact  with  a  large  surface 
of  acid,  which  eagerly  robs  it«of  any  watery  vapor  with  which  it  may 
be  loaded.  Into  the  bulb  of  the  tube,  c,  put  about  15  g.  (!  oz.)  of  the 
black  oxide  of  copper.  Weigh  the  tube  and  its  contents  very  care- 
fully, make  a  note  of  the  weight  and  connect  c  with  the  delivery 
tube  of  a.  Fill  the  U-tube,  d,  with  calcium  chloride,  weigh  this  tube 
and  its  contents  very  carefully,  make  a  note  of  the  weight  and  con- 


FIG.   16. 

nect  d  with  c,  as  shown  in  Fig.  16.  The  connections  with  c  may 
be  made  with  perforated  corks.  In  all  of  the  weighings,  remove 
the  corks  and  connecting  tubes.  Pass  H  from  the  gas  holder 
through  the  apparatus  until  it  is  delivered  from  d  unmixed  with  air. 
Then  bring  a  small  flame  under  the  bulb  of  c.  Notice  that  the 
copper  oxide,  when  heated  in  H,  changes  in  color  from  black  to 
red,  and  that,  near  the  end  of  c,  is  formed  a  dew  which  subsequently 
disappears.  Continue  the  operation  until  the  contents  of  the  bulb 
remain  red  when  the  lamp  is  removed  and  the  flow  of  gas  checked 
by  the  stop-cock  of  the  gas  holder.  When  the  apparatus  has  cooled, 
disconnect  the  parts,  carefully  weigh  c  with  its  contents,  and  d  with 
its  contents,  and  note  the  weights.  We  shall  find  that  the  contents 
of  c  have  lost  in  weight  and  that  those  of  d  have  gained,  the  gain 
at  d  being  about  |  greater  than  the  loss  at  c.  In  the  meantime,  the 
copper  oxide  has  been  changed  to  metallic  copper.  In  technical 
phrase,  the  copper  oxide  was  "  reduced"  by  the  H. 


26  HYDROGEN.  §  26 

26.  Purification.— The  materials  used  in  the  gen- 
eration of  hydrogen  are  seldom  free  from  impurities.  In 
consequence,  the  hydrogen  is  frequently  mixed  with  car- 
bon dioxide  (C02)  and  hydrogen  sulphide  (H2S),  as  well 
as  watery  vapor.  These  impurities  njay  be  removed  by 
passing  the  gas  through  a  series  of  bottles,  as  shown  in 
Fig.  17,  in  which  a  contains  lime-water  or  a  solution  of 


FIG.  17. 

caustic  soda  (§  270) ;  b,  a  weak  solution  of  silver  nitrate  ; 
c,  lumps  of  charcoal  (§  188) ;  and  d,  strong  sulphuric 
acid,  calcium  chloride,  or  other  drying  material.  If  the 
gas  is  to  be  collected  over  water,  the  last  bottle  is  of  no 
use. 

27.  Uses. — On  account  of  its  lightness,  hydrogen  has 
been  used  for  the  inflation  of  balloons.     On  account  of 
the  intense  heat  produced  by  its  combustion,  it  is  used  for 
melting  platinum  (§  397)  and  other  refractory  substances 
and  in  producing  the  calcium  light   (Exp.  49).     As  we 
have  seen,  it  is  useful  in  reducing  metallic  oxides,  the 
metals  thus  formed  being  remarkably  free  from  impurities. 

28.  Tests. —Hydrogen  is  easily  identified  by  its  physi- 
cal properties,  especially    its  lightness,  its  ready  inflam- 
mability and  the  extinction  of  a  taper  flame  placed  in  it. 


30  OXYGEN.  27 


OXYGEN. 

Symbol,  0 ;    specific  gravity,  16 ;  atomic  weight,  1G  m.  c. ; 
molecular  weight,  32  in.  c.  ;  quant  ivalence,  2. 

29.  Occurrence.— Of  all  the  elements,  oxygen  is 
the  most  abundant  and  the  most  widely  diffused.  One- 
fifth  of  the  air,  by  weight,  is  free  oxygen,  and  eight- 
ninths  of  water,  by  weight,  is  combined  oxygen.  It  has 
been  estimated  that  three-fourths  of  the  animal  world, 
four-fifths  of  the  vegetable  world,  one-half  of  the  min- 
eral world,  and  fully  two-thirds  of  the  whole  world  is 
oxygen. 

Note.—  The  word  oxygen  is  derived  from  the  Greek  oxus  (=acid) 
and  gennao  (=1  produce).  The  name  arose  from  the  erroneous  belief 
that  oxygen  is  a  necessary  constituent  of  an  acid.  The  element 
studied  in  the  last  section  has  a  better  claim  to  the  title  of  "  acid- 
former,"  but  there  is  little  probability  that  either  of  the  names  will 
ever  be  changed. 

3D.  Preparation. — Oxygen  is  generally  prepared  by 
the  decomposition  of  potassium  chlorate  by  heat.  Pul- 
verize 5  #.  of  clean  potassium  chlorate  (KCI03)  and  mix 
it  thoroughly  with  an  equal  weight  of  black  oxide  of 
manganese  (Mn02)  that  has  been  previously  heated  to  red- 
ness and  allowed  to  cool.  Place  the  mixture  in  an  igni- 
tion tube  (App.  4,  a)  of  such  size  that  the  tube  will  be 
not  more  than  a  third  full.  Close  the  tube  with  a  per- 
forated cork,  carrying  a  delivery  tube.  Support  the  igni- 
tion tube  in  a  slanting  position  and  apply  heat,  as  shown  in 
Fig.  18  (p.  28).  The  upper  part  of  the  mixture  should  be 


28 


OXYGEN. 


30 


heated  first  and  the  heat  so  regulated  that  the  evolution 
of  gas  shall  be  nearly  uniform.  Collect  the  gas  over  water 
in  bottles  of  about  250  cu.  cm.  (|  pt.)  capacity.  The  first 


- 


FIG.  18. 

half  bottle  full  of  the  gas  may  well  be  rejected.  Why  9 
Eemove  the  end  of  the  delivery  tube  from  the  water,  or, 
better  still,  break  the  connection  at  c  before  removing  the 
lamp.  Why  ? 

As  soon  as  it  is  convenient,  fill  one  of  the  larger  gas 
holders  with  oxygen.  For  this  purpose  it  will  be  better  to 
use  larger  quantities  of  the  materials,  and  heat  them  in  a 
flask.  This  flask  may  be  of  glass,  but  a  retort  of  copper 
or  iron,  expressly  constructed  for  the  purpose,  is  desirable 
in  every  laboratory.  (See  App.  22.) 

Caution. — Commercial  MnO»  is  sometimes  adulterated  with  carbon. 
When  such  a  mixture  is  heated  with  KCI03,  it  gives  rise  to  danger- 
ous explosions.  Hence,  a  new  or  doubtful  sample  may  well  be  tested 
on  a  small  scale  by  heating  it  with  KCI03  in  a  test-tube. 

31.vThe  Reaction. — At  the  close  of  the  process  just 
described,  the  ignition-tube  will  contain  manganese  diox- 
ide, (Mn02,  black  oxide  of  manganese)  and  potassium  chlo- 
ride (KCI).  The  KCI  is  easily  soluble  in  water;  the  Mn02 
is  not.  After  the  tube  has  cooled,  by  agitating  its  con- 


§  32       .  OXYGEN.  20 

tents  with  water  and  filtering,  the  Mn02  may  all  be  recovered 
unchanged.  It  suffered  no  chemical  chajige  and  was  used 
only  because,  in  some  way  still  obscure,  it  caused  the 
KCI03  to  decompose  more  quietly  and  at  a  lower  tempera- 
ture. Powdered  glass  or  fine  sand  might  be  used  with 
similar  results.  This  effect,  produced  by  what  seems  to 
be  the  mere  presence  of  a  substance,  has  been  called 
catalysis. 

2KCI03+2Mn02  =  2KCI  +  2Mn02  +  302, 
or 2KC103  =  2KCI+302. 

(a.)  Pure  KCI03  needs  to  be  heated  to  350°  C.  to  decompose  it ; 
when  mixed  with.  Mn02,  the  KCI03  decomposes  at  200°  C.  It  has 
been  suggested  that  the  Mn02  is  capable  of  a  higher  degree  of  oxida- 
tion, and  that  the  higher  oxide  easily  parts  with  some  of  its  0,  form- 
ing again  the  lower  oxide.  In  this  way  the  Mn03  would  act  as  a 
carrier  of  0,  taking  it  from  the  KCI03  and  then  setting  it  free.  (Com- 
pare §  149,  d.)  But  this  is  mere  hypothesis. 

32.  Physical  Properties.— Oxygen  is  a  transpar- 
ent, colorless,  tasteless,  odorless  gas,  not  to  be  distinguished 
by  its  appearance  from  hydrogen  or  ordinary  air.  It  re- 
fracts light  less  powerfully  than  air.  One  liter  of  it  (under 
ordinary  conditions  of  temperature  and  atmospheric  pres- 
sure) weighs  16  criths  or  1.43  g.  As  it  is  about  one-tenth 
heavier  than  air,  it  may  be  collected  by  downward  dis- 
placement, but  it  is  more  satisfactorily  collected  over  water. 
It  is  only  sparingly  soluble  in  water,  100  volumes  of  the 
liquid  absorbing  about  three  of  the  gas.  Like  hydrogen, 
it  has  recently  been  liquefied  by  subjecting  it  to  high 
pressure  and  low  temperature. 

Note.— The  bottles  containing  the  0  for  the  experiments  imme- 
diately following  should  be  prepared  by  grinding  their  lips  flat  with 
emery  powder,  as  described  in  App.  4,  h.  Have  ready  several  greased 


30  OXYGEN.  §  32 

/s  glass  plates  with  which  to  close  the  mouths  of  the  bottles 
thus  prepared.  During  the  combustions,  it  will  be  well  to 
keep  the  mo'uths  of  the  bottles  covered  loosely,  as  with  card- 
board. 

Experiment  32. — Repeat  Experiment  14,  holding  the  bot- 
tle right  side  up,  and  allow  the  taper  to  burn  until  the  flame 
dies  out.  Remove  the  taper  and  cover  the  mouth  of  the 
bottle.  Label  the  bottle  "  No.  1." 

FIG.  19.  Experiment  33'. — Into  a  second  bottle  of  the  gas,  thrust  a 
splinter  of  dry  wood,  having  a  glowing  spark  at  its  end. 

When  aflame,  withdraw  it,  blow  out  the  flame  and  repeat  until  the 
gas  fails  to  rekindle  the  splinter.  Cover  the  mouth  of  the  bottle. 
Label  this  bottle  "  No.  2." 

Experiment  34. — Place  a  lighted  candle  on  a  stand  between  two 
boys,  A  and  B.  Let  B  fill  his  mouth  with  0  from  the  gas 
holder.  A  may  blow  out  the.  flame,  leaving  a  glowing  wick  ;  ,5  may 
then  puff  0  upon  the  wick  and  relight  it.  Repeat  the  experiment 
until  the  mouthful  of  0  is  exhausted.  B  need  not  inhale  the  0,  but 
if  a  little  does  get  into  his  lungs  it  will  do  no  harm. 

Note.  — If  convenient,  perform  the  next  six  experiments  in  a  dark- 
ened room. 

Experiment  35. — Secure  a  piece  of  charcoal  made  from  oak  or  other 
bark,  if  you  can;  otherwise  use  charcaal  made  from  j 

wood.  Around  the  charcoal,  wind  one  end  of  a 
fine  wire,  to  form  a  handle.  Have  ready  a  bottle 
containing  a  liter  or  more  of  0.  Ignite  the  charcoal 
at  the  lamp  and  thrust  it  into  the  bottle.  Brilliant 
combustion  will  take  place  and  continue  until  all 
of  the  charcoal,  or  all  of  the  0,  is  consumed. 
Cover  the  bottle  as  before,  and  label  it  "  No.  3." 

Experiment  36. — Place  a  bit  of  sulphur  (brim- 
stone) the  size  of  a  pea  into  a  deflagration  spoon  FIG.  20. 
(App.  19)  and  hold  it  in  the  lamp-flame.  It  soon  melts  and  then 
takes  fire.  While  burning,  thrust  it  into  a  good  sized  jar  of  0.  It 
will  burn  with  a  beautiful  blue  flame  and  much  more  brilliantly 
than  it  did  in  the  air.  At  the  end  of  the  experiment,  cover  the 
jar  and  label  it  "  No.  4." 


§  32  OXYGEN.  31 

Caution. — Phosphorus  should  not  be  handled  with  naked,  dry 
fingers.  It  ignites  easily  by  friction  or 
slight  elevation  of  temperature.  Phos- 
phorus burns  are  serious.  Under 
water,  it  may  be  handled  and  even 
cut  with  safety.  When  taken  directly 
in  the  fingers,  the  fingers  should  be 
wet. 


Experiment  37.— A.  larger  glass  ves- 
sel is  desirable  for  this  experiment.  A 
good-sized  bell  glass,  such  as  is  used  frIG.  21. 

in  air  pump  experiments,  or  a  globe, 

such  as  is  used  for  keeping  gold-fish,  will  answer  well.  In  the 
middle  of  a  large  plate  or  tray  containing  water  4  or  5  cm.  deep, 
place  a  metal  support  rising  several  cm.  above  the  surface  of  the 
water.  From  a  stick  of  phosphorus,  cut,  under  water,  a  piece  the 
size  of  a  large  pea,  dry  it  thoroughly  between  pieces  of  blotting 
or  filter  paper,  place  it  upon  the  support  in  the  tray,  ignite  it  with  a 
hot  wire  and  quickly  invert  over  it  the  bell  glass  or  globe  of  0. 
The  combustion  is  exceedingly  energetic  and  indescribably  brilliant. 
The  metal  support  for  the  phosphorus  may  be  protected  from  combus- 
tion by  coating  its  upper  surface  with  lime,  chalk,  or  plaster  of  Paris. 
The  experiment  has  been  called  the  "Phosphoric  Sun."  At  first, 
part  of  the  gas  may  bubble  out  at  the  mouth  of  the  globe,  but  as  the 
dense  fumes  formed  by  the  burning  of  the  phosphorus  are  absorbed, 
water  will  rise  within  the  vessel.  Then  pour  more  water  into  the 
tray,  if  necessary,  and  label  the  globe  "No.  5." 

Experiment  38. — Heat  an  iron  rod,  as  thick  as  an  ordinary  lead 
pencil,  to  bright  redness.  Bring  it  quickly  in  front  of  a  jet  of  0 
from  the  gas  holder.  It  will  burn  with  beautiful  effects,  throwing 
off  sparks  and  dropping  globules  of  iron  oxide. 

Experiment  39,  —  Form  a  spiral  of  fine  iron  wire  (piano-forte  wire 
is  preferable)  by  winding  the  wire  upon  a  lead  pencil  or  piece  of 
glass  tubing  ;  wind  some  waxed  thread  upon  the  lower  end  of  the 
wire,  or  dip  the  end  of  the  wire  into  melted  sulphur  so  that  a  small 
sulphur  bead  shall  adhere  to  the  wire.  At  the  bottom  of  a  vessel 
containing  2  or  3  liters  of  0  place  a  layer  of  water  or  sand.  Ignite 
the  thread  or  sulphur  and  quickly  place  the  wire  in  the  0.  The 
burning  wax,  or  sulphur,  heats  the  end  of  the  wire  to  redness.  The 
wire  then  burns  with  beautiful  scintillations.  The  experiment 


OXYGEN. 


§32 


may  be  made  more  brilliant  by  using  a  coiled  watch  spring  instead 

of  the  iron  wire.  The  watch 
spring,  which  may  be  had 
gratis  of  almost  any  jeweler, 
is  to  be  softened  by  heating 
it  to  redness  and  allowing 
it  to  cool  slowly  ;  it  may 
then  easily  be  coiled.  Wind 
the  lower  end  of  the  spring 
with  twine  and  dip  it  into 
melted  sulphur,  to  prepare 
the  kindling  material.  The 
kindling  matter  should  be 
no  larger  in  quantity  than  is 
necessary  to  heat  the  wire  or 
spring  to  the  necessary  tem- 
perature ;  any  excess  inter- 
feres with  the  success  of  the 
experiment,  by  consuming 
the  free  O  and  forming  un- 
desirable compounds  in  the  jar.  The  melted  metal  globules  some- 
times fuse  their  way  into  or  through  the  glass  bottom  of  the  jar, 
when  the  water  or  sand  is  not  provided  to  prevent  such  a  result. 

Experiment  40. — Blow  a  jet  of  0  into  the  flame  of  an  alcohol  lamp. 
In  the  flame  thus  produced  hold  a  piece  of  watch  spring  or  steel 
wire.  It  will  burn  with  brilliant  scintillations. 

Experiment  1+1. — Into  bottle  No.  1,  put  a  piece  of  moistened  blue 
litmus  paper;  it  will  be  reddened.  Now  pour  in  a  little  clear 
lime  water  (slacked  lime  dissolved  in  water),  cover  the  mouth  of 
the  bottle  tightly  with  the  palm  of  the  hand  and  shake  the  bottle 
vigorously  ;  a  partial  vacuum  will  be  formed  (Exp.  190)  and  the 
clear  lime  water  will  become  turbid  and  soon  yield  a  white  pre- 
cipitate. The,  reddening  of  the  blue  litmus  paper  shows  the  presence 
of  an  acid.  The  colorless  gas  formed  by  the  burning  of  the  taper 
in  0  has  united  with  the  water  to  form  an  acid.  What  is  this 
colorless  gas  ?  The  turbidity  of  the  lime  water  and  the  precipitate 
(§  200)  show  that  it  is  carbon  dioxide  (C02),  sometimes  called 
carbonic  anhydride,  but,  more  frequently,  carbonic  acid  gas.  The 
carbon  (symbol  =  C)  of  the  taper  united  with  the  0  (synthesis) :. 
C  +  03  =  COo. 

Experiment  42. — Try  the  contents  of  jars  Nos.  2  and  3  with  a 
lighted  taper.  The  flame  is  extinguished  as  promptly  as  it  would 


§  34  OXYGEN.  33 

be  by  water.  Numerous  gases  act  in  this  way.  We  have  seen 
that  H-  extinguishes  flame  ;  but  this  gas  is  not  kindled  as  we 
know  that  H  would  be.  Try  the  contents  with  moistened  blue 
litmus  paper.  The  paper  is  reddened.  Have  you  any  idea  of  what 
the  gas  is?  Try  the  gas  with  clear  lime  water.  We  have  the 
turbidity,  etc.,  as  before.  What  do  you  now  think  the  gas  is  ?  The 
dry  wood  burned  in  No.  2  was  largely  carbon,  and  the  charcoal 
burned  in  No.  3  was  nearly  pure  carbon.  In  either  case, 


Experiment  43-  —  Test  the  contents  of  jar  No.  4  with  a  lighted 
taper.  The  flame  is  promptly  extinguished  as  before.  Test  with 
the  moistened  blue  litmus  paper.  The  paper  is  reddened  as  before. 
What  does  this  reddening  show  ?  Does  the  jar  contain  H  ?  Does  it 
contain  0  ?  Do  you  think  that  it  contains  carbon  dioxide  ?  Why  ? 
Test  with  clear  lime  water.  Does  it  contain  carbon  dioxide  ?  How 
was  this  gas  formed  ?  Was  any  carbon  used  in  its  production  ?  The 
gas  is  sulphur  dioxide  (S03)  sometimes  called  sulphurous  anhy- 
dride or  sulphurous  acid  gas  (§  144).  Write  the  reaction  for  its 
formation.  The  symbol  for  sulphur  is  S. 

Note.  —  If  a  very  little  of  the  SO.,  be  inhaled,  it  will  be  quickly  rec- 
ognized as  the  irritating  gas  familiar  to  all  from  the  use  of  sulphur 
matches.  If  we  turn  to  jar  No.  5  we  shall  find  that  the  phosphoric 
oxide  (P205)  formed  by  the  combustion  of  the  phosphorus  was  dis- 
solved in  the  water.  If  this  water  be  tested  with  blue  litmus  paper 
it  will  be  found  to  have  acid  properties.  We  have  thus  formed 
oxides  of  carbon,  of  sulphur  and  of  phosphorus,  and  seen  that  these 
oxides  unite  with  water  to  form  acids  (§  163).  If  the  litmus  paper 
used  in  testing  these  gases  had  been  dry  instead  of  wet  it  would  not 
have  been  reddened.  The  oxide  of  iron  (Fe304)  formed  in  experi- 
ments 38  and  39,  are  solid  and  insoluble  in  water. 

33.  Chemical   Properties.  —  Oxygen  is  chiefly 
marked  by  its  great  chemical  activity.    It  enters  into  com- 
bination with  all  the  elements  except  fluorine  (§  120).     In 
the  ordinary  use   of  the   term,  combustion   is  chemical 
union  with  oxygen  with  the  resulting  phenomena  of  heat 
and  light. 

34.  Uses.  —  Oxygen  is  used  in  countless  ways  in  the 
laboratories  of  Nature  and  of  man.     It  is  essential  to  the 


34  OXYGEX.  §  34 

processes  of  animal  respiration,  ordinary  combustion,  fer- 
mentation and  decay.  It  is  used  in  the  arts  to  increase 
the  intensity  of  combustion  for  purposes  of  heat  and  light, 
and  in  medicine  as  an  anesthetic. 

Experiment  44.  —  Fill  the  lungs 
with  air.  Slowly  exhale*  the  air 
through  a  tube  so  that  the  air  shall 
bubble  up  through  clear  lime  water 
in  a  clear  glass  bottle.  The  lime- 
water  quickly  becomes  turbid,  as  in 
Ex  p.  41,  showing  that  C03  is  one 
of  the  products  of  respiration. 

35.  Relation  to  Ani- 
mal Life. — All  animal  crea- 
tures are  adapted  to  the  absorp- 
tion of  free  oxygen,  either  that 
of  the  air  or  that  held  in  solution  by  water.  The  oxy- 
gen, when  inhaled,  enters  into  chemical  combination 
with  various  parts  of  the  animal  structure,  and  is  then 
exhaled  as  C02-  We  thus  see  that  oxygen  is  necessary  to 
animal  life,  for  which  reason  it  was  formerly  called  vital 
air.  The  chemical  changes  occurring  in  the  animal  are 
the  same  as  those  exhibited  in  Experiments  32  and  33, 
excepting  so  far  as  rapidity  of  combustion  or  rigor  of 
chemical  activity  is  concerned.  The  heat  thus  evolved 
(Ph.,  §  674,  e)  keeps  the  temperature  of  the  body  above 
that  of  surrounding  inanimate  objects;  when  this  chemi- 
cal action  ceases  (death),  the  temperature  of  the  body  falls 
to  that  of  its  surroundings.  When,  by  any  means,  the  sup- 
ply of  oxygen  is  cut  off,  this  chemical  action  is  arrested 
and  the  victim  dies.  This  effect  may  follow  from  chok- 
ing, drowning,  or  the  inhalation  of^even  non-poisonous 
gases  that  contain  no  free -oxygen,  as  hydrogen  or  ni- 


§  37  OZONE.  35 

trogen.  These  do  not  poison;  they  suffocate.  Every 
part  of  every  animal  is  being  continually  burned  up  by 
oxygen.  Unless  the  loss  be  made  good  by  proper  food, 
emaciation  and  final  death  must  follow.  As  we  shall  soon 
see,  common  air  is  diluted  oxygen.  An  animal  breath- 
ing pure  oxygen  can  not  live  long,  because  it  lives  so 
fast;  there  are  undue  excitement,  over  action,  fever  and 
speedy  death. 

Experiment  45. — Into  a  large  test  tube  filled,  over  water,  with 
nitric  oxide  (NO,  §  83)  pass  a  small  quantity  of  0.  The  two  color- 
less gases  combine  eagerly,  forming  dense  red  fumes,  which  are 
rapidly  dissolved  in  the  water. 

Experiment  46. — Dissolve  a  piece  of  potassium  hydrate  (caustic 
potash,  KHO)  the  size  of  a  pea,  in  10  cu.  cm.  of  water  and  pour 
the  solution  into  a  long  test  tube  filled  with  O.  Add  a  few  flakes 
of  pyrogallic  acid.  Close  the  mouth  of  the  tube  with  the  thumb 
and  shake  the  contents.  The  liquid  will  be  blackened.  Place  the 
mouth  of  the  tube  under  water  and  remove  the  thumb.  Water  will 
rise  in  the  tube  to  fill  the  partial  vacuum  formed  by  the  absorption 
of  the  0  in  the  tube  by  the  liquid  mixture. 

36.  Tests. — Free  oxygen,  not  much  diluted  with  other 
gases,  is  most  easily  tested  by  plunging  into  it  a  glowing 
splinter,  as  in  Exp.  33.      The  only  other  gas  that  will 
thus  rekindle  the  splinter  is  nitrous  oxide  (laughing  gas, 
N20  ;  §  79).     This  test,  though  generally  enough,  is  not 
conclusive.    The  properties  of  oxygen,  illustrated  in  the 
last  two  experiments,  i.  e.,  that  of  forming  red  fumes  with 
nitric  oxide   and  of  blackening  a  mixture  of  dissolved 
potassium  hydrate  and  pyrogallic  acid  and  of  being  rapidly 
absorbed  thereby,  constitute  unmistakable  tests  for  the 
presence  of  free  oxygen. 

37.  Ozone.— In   addition   to   the  ordinary  form  of 
oxygen,  which  contains  two  atoms  in  each  molecule,  a  re- 


3G  OZONE.  §  37 

markable  variety  is  known  in  which  there  are  three  atoms 
to  each  molecule.  This  condensed  and  more  active 
form  of  oxygen  is  called  ozone.  In  changing  oxy- 
gen to  ozone  there  is  a  volumetric  condensation  of  one- 
third.  It  is  formed  at  the  -f  electrode  in  the  electrolysis 
of  water;  by  the  discharge  from  an  electric  machine 
through  air  or  oxygen;  or  by  the  slow  oxidation  of  phos- 
phorus in  moist  air,  etc.  It  is  best  prepared  by  electric 
apparatus  devised  for  that  purpose,  but  the  phosphorus 
or  ether  method  is  more  convenient. 

Experiment  47.  —  Prepare  a  cylinder  of  phosphorus  3  or  4  cm.  long, 
by  scraping  its  surface  clean  under  water.  (Remember  the  caution 
preceding  Experiment  37.)  Place  the  cylinder  in  a  clean  bottle  of 
1  or  2  liters  capacity,  and  pour  in  enough  water  to  half  cover  the  cyl- 
inder. Close  the  mouth  of  the  bottle  with  a  plate  of  glass  or  a  loose 
stopper,  and  set  the  bottle  in  a  warm  place  (20°  C.  or  30°  C.).  In  10  or 
15  min.,  notice  the  fog  above  the  phosphorus.  Allow  the  bottle  to 
remain  for  several  hours.  The  feeble,  chlorine-like  odor  of  ozone 
will  be  discernible.  A  still  more  convenient  method  is  to  place  a 
few  drops  of  ether  in  a  tall  beaker  glas?,  and  stir  the  quickly  formed 
vapor  with  a  hot  glass  rod. 

Experiment  48.  —  Prepare  two  slips  of  white  paper  by  dipping  them 
into  a  solution  of  starch  and  potassium  iodide  (Exp.  99).  Thrust 
one  of  these  into  a  bottle  of  O  ;  no  change  will  be  noticed.  Thrust 
the  other  test  paper  into  the  bottle  or  beaker  glass  containing  ozone  ; 
the  white  paper  will  be  promptly  colored  blue.  The  energetic 
ozone  displaces  the  iodine. 


The  free  iodine  colors  the  starch  blue.     (Exp.  122.) 

38.  Properties  of  Ozone.—  Ozone  has  been  pre- 
pared only  in  small  quantities,  but  it  manifests  its  presence 
by  its  peculiarly  energetic  action.  It  is  one  of  the  most 
powerful  oxidizing  agents  known.  It  is  unquestionably 
present  in  pure  country  and  sea  air,  and  noticeably  absent 


§  39  OZONE.  37 

in  the  atmosphere  of  large  cities,  where  its  oxidizing  in- 
fluence upon  organic  and  other  deleterious  matter  results 
in  partial  disinfection  and  its  own  transformation  into 
oxygen  and  oxygen  compounds.  In  its  oxidizing  action, 
its  volume  is  supposed  to  undergo  no  change,  the  third 
atom  of  the  ozone  molecule  (03)  entering  into  combination 
and  leaving  the  two  atoms  of  the  ordinary  oxygen  mole- 
cule (02).  It  is  changed  by  heat  into  ordinary  oxygen 
with  increase  of  volume,  the  change  being  instantaneous 
at  237°  C. 

(a.)  It  was  formerly  thought  that  ozone  had  its  counterpart  in  a 
form  of  oxygen,  having  one  atom  to  the  molecule,  and  called 
antozone.  "  Further  experiments  have,  however,  proved  that  ant- 
ozone  is  nothing  more  than  hydrogen  dioxide."  (§  44.) 

39.  Allotropism. — We  have  seen  that  ozone  mani- 
fests characteristics  decidedly  different  from  those  of  ordi- 
nary oxygen.  Still,  its  fundamental,  chemical  identity 
with  oxygen  is  unquestionable.  For  example,  the  potas- 
sium oxide  (K20)  that  it  formed  by  displacing  the  iodine 
of  the  potassium  iodide,  in  Experiment  48,  is  identical 
with  the  potassium  oxide  formed  in  any  other  way.  Tliis 
capability  of  existing  in  different  forms  with 
chemical  identity  undestroyed  is  called  allotropism. 
Ozone  is  an  allotropic  modification  of  oxygen. 


38  HYDROGEN  AND    OXYGEN.  §  40 


COMPOUNDS  OF  HYDROGEN  AND  OXYGEN. 

40.  Combustion  of  Hydrogen.— When  hydro- 
gen is  heated  to  the  temperature  of  about  500°  0.,  in  the 
presence  of  free  oxygen,  the  two  elements  enter  into  chemi- 
cal union,  forming  water  (H20).   This  was  shown  in  a  gen- 
eral way  in  Experiment  28.     Whatever  the  conditions 
winder  which  hydrogen  is  burned  in  oxygen  or  in  air, 
the  sole  prod^Lct  is  water.    This  is  true,  even  in  the 
combustion  of  a  compound  containing  hydrogen,  as  has 
been  previously  stated  (§  25).     The  clashing  together  of  the 
hydrogen  and  oxygen  atoms  involved  in  the  combustion 
(§  11)  develops  an  extraordinary  amount  of   heat   (Ph., 
§  472),  viz.,  34,462  heat  units;  i.  e.,  the  combustion  of  a 
given  weight  of  hydrogen  in  oxygen  develops  enough  heat 
to  warm  34,462  times  that  weight  of  water  from  0°  C.  to 
1°  C.,  or  more  than  62,000  times  that  weight  of   water 
from  32°  F.  to  33°  F.     The  experiments  in  this   section 
are  intended  to  set   forth  the   principal  features  of   the 
direct  synthesis  of  hydrogen  and  oxygen. 

41.  The  Compound  Blowpipe. — The  compound 
|«j|^^^^^^^^^^^/z  or   oxyhydrogen    blow- 

o  *  pipe  consists  of  a  double 

tube,    one    inside     the 

H  |  other,  as  shown  in  Fig. 

FIG.  24.  24.     The  interior  tube 

is  connected  by  rubber  tubing  with  the  oxygen  gas  holder  ; 

the  outer  tube,  with  the  hydrogen  gas  holder.     Hydrogen 


§  41  HYDROGEN  AND    OXYGEN.  39 

is  first  turned  on  and  ignited  at  a.  Oxygen  is  then  turned 
on  until  the  flame  is  reduced  to  a  fine  pencil.  The  pres- 
sure at  the  gas  holders  should  be  steady,  the  amount 
thereof  being  easily  determined  by  trial. 

Experiment  49. — Hold  bits  of  iron  and  copper  wire,  watch  springs, 
strips  of  zinc,  etc.,  in  the  flame  of  the  compound  blowpipe.  They 
will  be  readily  dissipated  with  characteristic  luminous  effects.  A  fine 
wire  of  platinum,  an  exceedingly  refractory  metal,  is  readily  melted, 
and  silver  can  be  thus  distilled.  A  piece  of  lime  or  chalk,  freshly 
scraped  to  a  point  and  held  in  the  flame,  is  heated  to  such  a  high 
degree  of  incandescence  that  it  produces  a  light  of  remarkable  in- 
tensity. This  is  essentially  the  Drummond  or  calcium  light.  The 
temperature  of  the  oxyhydrogen  flame  has  been  estimated  to  be 
above  2800°  C. 

Experiment  50.  —  Over 
the  jet,  a,  of  the  com- 
pound blowpipe,  slip  a 
piece  of  rubber  tubing 
Allow  both  gases  to  flow 
through  the  apparatus, 
and  dip  the  tubing  into  a 
metallic  dish  full  of  soap- 
suds until  a  mass  of  foam  FIG.  25- 
has  formed,  as  shown  in  Fig.  25.  Close  the  stop-cocks  at  the  gas 
holders  or  the  blowpipe,  remove  the  tubing  from  the  soap-suds,  and 
then  touch  the  foam  with  a  flame  carried  at  the  end  of  a  stick  about 
a  meter  in  length.  A  violent  explosion  will  take  place.  (See  §  22 
and  the  Note  following  Exp.  19.) 

Note.— It  you  have  no  compound  blowpipe,  introduce  one  volume 
of  0  and  two  of  H  into  a  gas  bag  or  small  gas  holder  (App.  13). 
The  gases  will  soon  become  thoroughly  mixed  by  diffusion,  when 
they  may  be  passed  into  the  soap-suds  through  the  rubber  tubing. 
Remember  that  this  mixture  is  dangerously  explosive  ;  be  sure  that 
there  is  no  possibility  of  flame  coming  into  contact  with  the  contents 
of  the  gas  bag  or  the  connected  tubing.  The  explosion  just  de- 
scribed was  free  from  danger,  because  the  restraining  wall  of  the 
explosive  mixture  was  only  a  thin  film  of  H20,  the  flying  fragments 
of  which  could  do  no  harm.  If  the  contents  of  your  gas  holder 
should  explode,  the  flying  fragments  would  probably  do  serious 


40 


HYDROGEN  AND    OXYGEN. 


damage.  It  is  advisable  to  throw  away  the  mixed  gases  that  may  re- 
main at  the  close  of  the  experiments  with  them.  Any  attempt  to 
burn  these  gases  previously  mixed,  even  as  they  issue  from  the  jet  of 
the  compound  blowpipe,  will  result  in  an  explosion. 

Experiment  51. — Repeat  Experiment  19,  using  the  mixed  gases 
instead  of  H  and  guarding  carefully  against  an  accidental  explo- 
sion. The  bubble,  or  a  mass  of  bubbles,  dipped  from  the  dish 
shown  in  Fig.  25,  may  be  safely  exploded  while  resting  in  the  palm 
of  the  hand. 

Note. — A  hydrogen  pistol  may  be  made  of  a  tin  tube  3  or  4  cm.  in 
diameter  and  15  or  20  cm.  in  length,  closed  at  one  end.  The  open 
end  is  to  be  fitted  with  a  cork,  and  the  closed  end  provided  with  a 
small  opening  the  size  of  a  pin  hole.  By  placing  the  thumb  over 
the  pin  hole,  the  pistol  may  be  filled  over  water  with  the  mixed  gases, 
the  cork  put  into  place,  and  the  pin  hole  presented  to  a  candle  or 
lamp  flame.  The  cork  is  the  bullet  of  this  pistol.  The  pistol  may 
be  partly  filled  with  H  by  upward  displacement,  thus  providing  a 
mixture  of  H  and  air,  that  is  less  violently  explosive  because  of  the 
dilution  of  the  0  of  the  atmosphere. 

Experiment  52. — A  tall  tin  cup  filled  with  a  detonating  mixture  of 
H  and  0  may  be  inverted  over  a  piece  of  platinum  sponge.  The 
sponge  may  be  supported  a  few  inches  above  the  table  by  the  wire 
used  in  Exp.  30.  In  a  few  moments  the  mixed  gases  will  be  ex- 
ploded. 

4r2.  The  Eudiometer.— The  eudiometer  is  an  in- 
strument for  determining  the  propor- 
tions in  which  gases  unite.  It  consists 
of  a  strong  glass  tube  with  two  plati- 
num wires  fused  into  the  sides,  near 
the  closed  end.  The  wires  nearly 
touch  within  the  tube.  One  of  the 
most  common  forms,  devised  by  Ure, 
consists  of  a  IT- tube  with  the  closed 
arm,  I,  graduated  to  cubic  centimeters. 
It  is  represented  in  Fig.  26. 


FIG.  26. 


§  42  HYDRO  UKX  AX  I)    OXYGJKX.  41 

Experiment  53. — Fill  the  eudiometer  with  water  and  hold  it  with 
the  open  arm,  a,  horizontal,  under  water  and  under  the  closed  arm,  6. 
By  means  of  a  rubber  tube  carrying  a  short  piece  of  glass  tubing 
drawn  out  to  a  fine  jet,  pass  about  20  cu.  cm.  of  pure  0  from 
the  gas  holder  into  b.  Be  sure  that  the  air  had  been  previously 
driven  out  of  the  delivery  tube  ;  make  the  measurement  with  th  > 
eudiometer  erect  and  the  water  standing  at  the  same  level  in  both 
tubes.  Water  may  be  removed  from  a,  if  necsssary  to  this  end, 
by  means  of  a  pipette  (App.  5.)  Now  introduce  about  50  cu.  cm, 
of  pure  H  into  b,  and  note  the  exact  amount  of  gas  therein  ar; 
before.  It  may  prove  difficult  to  introduce  exactly  20  and  50  cu.  cm. 
A  little  variation  matters  not,  provided  that  you  measure  accurately 
the  amounts  actually  introduced,  and  that  the  volume  of  the  H 
is  more  than  twice  that  of  the  0.  Suppose  that  the  first  measure- 
ment shows  21  cu.  cm.  of  0,  and  that  the  second  shows  75  cu.  cm. 
of  mixed  gases.  Then  you  have  introduced  54  cu.  cm.  of  H. 
Close  the  opcm  end  firmly  with  the  thumb,  leaving  a  cushion  of  air 
between  it  and  the  surface  of  the  water,  as  shown  in  Fig.  26.  Pro- 
duce an  electric  spark  between  the  ends  of  the  platinum  wires  in  the 
mixed  gases.  [Ph.,  §  371  (21),  (33),  (35),  §  411.]  The  spark  pro- 
duces combination  between  the  0  and  part  of  the  H.  On  removing 
the  thumb  and  bringing  the  liquid  surfaces  to  the  same  level,  it  will 
be  found  that  there  are  only  12  cu.  cm.  of  gas  in  b.  By  filling  a  with 
water  and  closing  it  with  the  thumb,  the  gas  may  be  easily  passed 
from  b  into  a,  and  thence,  under  water,  to  a  convenient  vessel  for 
testing.  It  will  be  found  to  be  pure  H.  The  21  cu.  cm.  of  0  has 
united  with  42  cu.  cm.  of  H  to  form  a  minute  quantity  of  H2O,  leav- 
ing the  12  cu.  cm.  of  H  because  there  was  no  0  with  which  it  could 
unite.  See  §  12.  If  the  eudiometer  had  been  kept  at  a  tempera- 
ture above  100°  C.,  or  212°  F.,  and  the  gases  confined  by  mercury 
instead  of  water,  b  would  have  contained  42  cu.  cm.  of  steam  and 
12  cu.  cm.  of  H.  The  volume  of  steam  would  be  the  same  as  that 
of  the  H  that  entered  into  its  composition.  The  combination  was 
accompanied  by  a  diminution  of  volume  equal  to  that  of  the  0  enter- 
ing into  chemical  union.  In  other  words,  three  volumes  shrink  to 
two  volumes  in  the  process  of  combination.  Representing  equal 
volumes  of  the  gases  by  equal  squares,  the  volumetric  composition 
of  H  2  0  and  the  condensation  j  ust  mentioned  may  be  represented  to 
the  eye  as  follows : 


42  SYDROGEN  AND   OX  TO  EN.  §  43 

As  0  is  16  times  as  heavy  as  H  [Ph.,  §  253  (3)],  the  one  volume  of 
O  weighs  8  times  as  much  as  the  two  volumes  of  H.  Hence,  we  see 
that  the  gravimetric  composition  of  water  is  8  parts  of  0  to  1  of  H, 
as  previously  stated. 

Experiment  54. — Support  a  wide  tube  of  clear  glass  in  a  vertical 

position.  A  bottomless  bottle,  the 
neck  of  a  broken  retort,  or  a  lamp- 
chimney  will  answer  well.  Through 
the  perforated  cork  that  closes  the 
upper  end,  pass  a  stream  of  H  from 
the  gas  holder.  When  the  air  has 
been  driven  out  of  the  bottle,  apply 
a  flame  at  the  lower  end  and  regu- 
late the  flow  so  that  the  gas  burns 
slowly  at  the  opening.  From 
another  gas  holder,  pass  a  current 
of  0  through  a  piece  of  glass  tubing 
drawn  out  to  form  a  small  jet.  As 
the  jet  passes  through  the  burning 
gas,  the  0  takes  fire  and  burns  in  an 
atmosphere  of  H. 

43.  Combustibles  and  Supporters  of  Com- 
bustion.— Since  all  ordinary  combustion  takes  place  in 
the  air,  which  furnishes  the  necessary  supply  of  oxygen,  it 
is  customary  to  speak  of  oxygen  as  a  supporter  of  combus- 
tion, and  the  hydrogen  or  other  substance  that  thus  unites 
with  the  oxygen  as  a  combustible.     The  experiment  just 
given  shows  that  this  distinction  has  no  reason  for  its  con- 
tinued existence  except  custom  and  convenience.     When 
oxygen   and  hydrogen   atoms  clash  together  in  chemical 
union,  we  have  combustion,  and  it  makes  no  difference 
whether  the  hydrogen   emerges  into   an  atmosphere    of 
oxygen,  or  the  oxygen  emerges  into  an  atmosphere   of 
hydrogen.     We  shall,  however,  continue  to  speak  of  burn- 
ing hydrogen  and  carbon  instead  of  burning  oxygen. 

44.  Hydrogen  Dioxide. — While  water,  H2O,  is  the  only 
compound  of  H  and  0  found  in  nature,  another  (H302),  containing 


§  44  HYDROGEN  AND   OXYGEN.  43 

twice  ns  much  0,  may  be  produced  by  chemical  means.  It  is  a 
sirupy,  colorless  liquid,  and  at  100°  C.  separates  into  H20  and  0  with 
almost  explosive  violence.  It  has  no  "  practical"  value,  but  is  of  con- 
siderable theoretical  importance.  It  may  be  considered  as  composed 
of  two  groups  of  HO  ;  thus,  (HO)—  (HO).  This  group  is  called  hy- 
droxyl.  Hydrogen  dioxide,  or  peroxide,  (H0)2,  is  sometimes  called 
free  hydroxyl.  (§  97.) 

Ac 

EXERCISES. 

•  • 

1.  What  is  the  difference   between  a  chemical   and  a  physical 
change  ?    Make  your  answer  as  explicit  as  you  can,  and  illustrate. 

2.  (a.)  Describe  briefly  the  common  method  for  the  preparation  of 
0,  omitting  no  essential,     (b.)  Tell  what  you  can  of  H  and  its  prepa- 
ration. 

3.  (a.  )  Give  the  symbol,  atomic  weight  and  chemical  properties  of  O. 
(&.)  What  is  meant  by  oxidation  ? 

4.  (a.)  What  is  an  element  ?    (&.)  How  many  are  known  ?    (c.)  Wliat 
gases  enter  into  the  composition  of  water?    (d.)  Prove  your  answer 
in  two  ways,  one  method  being  the  reverse  of  the  other,     (e.)  What 
name  do  you  give  to  each  method  ? 

5.  When  a  current  of  steam  is  passed  through  an  iron  tube  nearly 
filled  with  bright  iron  turnings  or  filings,  the  tube  being  placed  across 
a  furnace  and  its  middle  portion  heated  to  redness,  large  quantities  of  a 
combustible  gas  that  may  be  collected  over  water  are  delivered  from 
the  tube,    (a.)  What  do  you  suppose  the  gas  to  be  ?    Why  ?    (6.)  Will 
the  iron  turnings  in  the  tube  weigh  more  or  less  at  the  end  of  the 
experiment  than  they  did  at  the  beginning?     Why  ? 

6.  (a.)  How  many  hydrogen  oxides  are  known?    Name  them.     De- 
fine chemistry.     (b.)  What  is  the  difference  between  chemistry  and 
physics  ? 

7.  (a.)  What  is  the  distinction  between  organic  and  inorganic  com- 
pounds ?    (6.)  Between  a  mixture  and  a  compound  ? 

8.  («.)  If  240  cu.  cm.  of  H  and  120  cu.  cm.  of  0  be  made  to  com- 
bine, what  will  be  the  name  of  the  product?    (b.)  If  the  experiment 
be  performed  in  a  vessel  having  a  temperature  above  that  of  boiling 
water,  what  will  be  the  name  and  volume  of  the  product  ? 

9.  If  300  cu.  cm.  of  steam  be  condensed  to  water  and  the  water 
decomposed  (Exp.  12),  what  will  be  the  volume  and  composition  of 
the  product  ?  *  0. 

10.  (a.)  What  weight  of  His  there  in  8,064^.  of  H20?    (b.)  What 
volume  of  H  ?    (c.)  What  is  a  crith  ?      -  b  ,.  $4  //  . 


44  BYDROUEX  Axn  OXYGEX.  §  44 

11.  Give  a  possible  explanation  for  the  fact  that  recently  heated 
but  cool  platinum  sponge  will  explode  a  mixture  of  H  and  0. 

12.  What  is  meant  by  the  reduction  of  copper  oxide  ? 

13.  How  could  you  tall  0  f  ran  H  ? 

14.  State  tha  principal  difference  between  ordinary  0  and  its  allo- 
tropic  modification. 

15.  (a.)  If  a  mixtme  of  50  cu.  cm.  of  H  and  50  cu.  cm.  of  0  be   , 
exploded  in  an  eudiometer,  what  will  be  the  name  and  volume  of  JjH 
the  remaining  gas?    (5.)  What  precaution  must  be  taken  in  measur- 
ing the  gases  ? 


AIR     AND     ITS     CONSTITUENTS 


I. 


AIR. 


45.  Occurrence.  —  The  earth  is  surrounded  by  an 
atmosphere  of  air  extending  to  a  height  variously  esti- 
mated at  from  50  to  200  miles. 

Experiment  55.  —  Repeat  Experiments  45  and  43,  using  common  air 
instead  of  0.  These  tests  show  the  presence  of  free  0  in  the  air. 

Experiment  56.  —  When  mercury  (Hg)  is  heated  in  air  it  is  gradually 
changed  into  red  oxide  of  mercury  (red  precipitate).  The  mercury 
oxide  weighs  more  than  the  mercury  used,  showing  that,  though  it 


FIG.  28. 


may  have  lost  something  in  the  process,  it  has  more  than  made  good 
any  such  imaginary  loss  by  the  gain  of  something  from  the  air.  The 
process  is  slow  and  you  would  better  buy  the  oxide.  Put  about  10  g. 


All?. 


§45 


of  this  red  mercury  oxide  into  an  ignition-tube  20  cm.  long,  provided 
with  a  perforated  cork  and  delivery -tube.  Close  the  tube  and  sup- 
port it  over  the  lamp-flame  in  some  such  way  as  that  shown  in  Fig. 
28.  The  ignition-tube  should  be  in  an  oblique  position  so  as  to  ex- 
pose at  least  3  or  4  cm.  of  its  length  to  the  flame.  As  the  mercury 
oxide  becomes  heated,  gas  will  be  delivered  and  may  be  collected  over 
water  in  small  bottles.  The  first  bottle-full  collected  should  be  thrown 
away,  as  it  contains  the  air  that  was  in  the  apparatus  at  the  begin- 
ning of  the  experiment.  When  the  gas  is  no  longer  delivered  freely, 
remove  the  delivery-tube  from  the  water,  wipe  the  adhering  liquid 
from  it,  and  then  remove  the  lamp.  By  testing  the  gas  on  hand  you 
will  see  that  it  is  0.  The  0  came  from  the  mercury  oxide,  to 
form  which  it  was  given  up  by  the  air.  At  the  close  of  the  experi- 
ment, minute  globules  of  metallic  mercury  will  be  found  upon  the 
sides  of  the  upper  part  of  the  ignition-tube.  With  proper  apparatus, 
the  experiment  might  be  continued  until  all  of  the  mercury  oxide 
disappeared,  leaving  behind  only  metallic  mercury.  The  synthesis 
of  Hg  and  0  gave  us  the  oxide;  the  analysis  of  the  oxide  gave  us 
back  the  identical  atoms  of  Hg  and  0. 

Experiment  57. — At  one  end  of  the  beam  of  a  balance,  suspend  a 
long  vertical  tube,  a,  containing  a  taper,  and  a  bent  tube,  c,  con- 
taining potassium  hydrate  (caustic  potash,  KHO).  The  taper  may 


FIG.  29 


§  45 

be  supported  on  a  cork,  perforated  so  as  to  admit  air  freely  to  a, 
which  should  be  about  4  cm.  in  diameter.  Connect  the  two  tubes  by 
a  piece  of  rubber  tubing  and  equipoise  them  and  their  contents  by 
weights  at  w.  Instead  of  equipoising  the  tubes,  they  may  be  weighed 
carefully,  before  and  after  the  experiment,  as  in  Exp.  31.  Connect 
the  tube,  c,  with  a  gas  holder,  g,  filled  with  HaO,  which  on  being 
allowed  to  escape  at  i  produces  a  current  of  air  through  the  tubes, 
and  thus  maintains  the  combustion  of  the  taper,  which  should  now 
be  lighted.  The  head  of  H20  in  the  aspirator,  g,  and  the  size  of  the 
connecting  tubes  should  be  such  as  to  produce  a  strong  current 
through  the  apparatus.  In  addition  to  lumps  of  KHO  in  c,  it  is  well 
to  fill  the  bend  of  c  with  an  aqueous  solution  of  KHO,  through  which 
the  gases  will  bubble.  The  H20  and  C02  (§  196),  formed  by  the 
combustion  of  the  H  and  C  of  the  taper,  are  absorbed  by  the  KHO. 
After  the  taper  has  burned  for  a  few  minutes,  the  tubes,  a  and  c,  are 
disconnected  from  the  gas  holder  and  allowed  to  hang  freely  from  the 
beam.  They  will  be  found  to  be  heavier  than  before  the  burning  of 
the  taper,  the  added  weight  being  that  of  the  0  of  the  air  that  has 
entered  into  combination  with  the  H  and  the  C  of  the  taper. 

Experiment  58. — Provide  a  cork  about  5  cm.  in  diameter  and  2  cm. 

in  thickness.  Cover  one  side  with 
a  thin  layer  of  plaster  of  Paris 
mixed  with  H30.  The  paste 
may  be  raised  near  the  edge  of 
the  cork  so  as  to  produce  a  concave 
surface.  Dry  the  cork  thoroughly 
and  you  have  a  convenient  capsule 
for  floating  upon  H20.  For  a 
single  experiment,  the  cork  may 
be  covered  with  dry  powdered 
chalk  or  lime.  Upon  this  capsule, 

pIG      Q  place  a  piece  of  phosphorus  that 

has  been  dried  by  wrapping  it  in 
blotting  or  filter  paper.  Float  the  capsule  upon  H20,  ignite  the 
phosphorus  with  a  hot  wire,  and  cover  it  with  a  bell-glass  or  other 
wide-mouthed  vessel.  While  the  phosphorus  is  burning,  hold  the 
bell  glass  down  with  the  hand.  The  phosphorus  combines  with  the 
O  of  the  air,  forming  dense  fumes  of  phosphoric  oxide  (P205).  These 
fumes  are  soon  absorbed  by  the  H2O,  which  rises  in  the  bell-glass 
to  occupy  the  space  vacated  by  the  O. 

Experiment  59. — When  the  fumes  of  P205  have  been  absorbed, 
slip  a  glass  plate   under  the  mouth  of  the  bell-glass  and  place  it 


48  AIR.  $J  46 

mouth  upward,  without  admitting  any  air.  If  the  bull-glass  be 
capped,  as  shown  in  Fig.  30,  it  need  not  be  removed  from  the  water- 
pan  ;  H20  should  be  poured  into  the  pan  until  the  liquid  outside  the 
receiver  is  at  the  same  level  as  that  inside.  Test  the  gaseous  contents 
with  a  lighted  taper.  The  flame  is  extinguished,  but  the  gas  does 
not  burn.  It  is  neither  0  nor  H.  It  is  nitrogen,  an  element  that 
we  shall  study  in  the  next  section. 

46.  Composition  of  Air.— Air  is  composed  chiefly 
of  oxygen  and  nitrogen.  Very  careful  determinations 
show  its  volumetric  and  gravimetric  composition  to  be  as 
follows : 

By  Volume.  By  Weight. 

Oxygen        .         .        20.9  %         .         .        23.1  % 
Nitrogen  .        .        .    79.1  •  76.9 


100.  100. 

This  composition  of  the  air  is  nearly  but  not  quite  con- 
stant at  diiferent  times  and  places.  The  air  also  contains 
small  quantities  of  carbon  dioxide  (C02).  more  or  less 
watery  vapor,  traces  of  ammonias,  etc. 

47.  Physical  Properties.— The  air,  when  pure,  is 
transparent,  colorless,  tasteless,  and  odorless.    Under  stand- 
ard conditions  (temperature,  0°C. ;  barometer,  760  mm.) 
a  liter  of  it  weighs  1.2932  g.  or  14.45  criths.     It  is  therefore 
14.45  times  as  heavy  as  hydrogen.     It  presses  upon  the 
surface  of  the  earth  with  a  force  of  1.033  Kg.  per  sq.  cm. 
or  15  Ib.  per  sq.  in.     (Ph.,  §§  273,  494.) 

48.  Chemical  Properties.— The  chemical  prop- 
erties of  air  are   those  of  its  several   constituents.     Its 
oxygen  supports  combustion,  the  energy  of  the  combus- 
tion being  checked  by  the  diluting  nitrogen.     Its  nitrogen 
manifests  all  of  the  properties  of    nitrogen.     Its   watery 
vapor  condenses  when  the  temperature  falls,  just  as  any 


§  49 

other  watery  vapor  would  do.  Hence,  we  have  dew  and 
frost.  When  a  stream  of  air  is  passed  through  lime-water, 
its  carbon  dioxide  renders  the  clear  liquid  turbid,  just 
as  carbon  dioxide  always  does  (Exp.  44). 

49.  Air  is  a  Mixture.— The  first  sentence  in  the 
preceding  paragraph  intimates  that  the  constituents  of  our 
atmosphere  are  not  chemically  united  but  merely  mixed ; 
that  each  of  them  is  free  (§  12).  This  fact  is  shown  by 
the  following  additional  considerations  : 

(a.)  When  the  constituents  are  mixed  in  the  proper  proportions 
they  form  air,  but  there  is  no  change  of  volume  or  manifestation  of 
heat,  light,  or  electricity. 

(6.)  The  composition  of  air  is  slightly  variable  (§  12). 

(c.)  Each  gas  dissolves  in  H20  independently  of  the  other.  When 
H,0  is  boiled,  it  loses  the  gases  it  held  in  solution.  Collection  and 
analysis  of  these  gases  show  that  they  are  32$  0  and  68  $>  nitro- 
gen. The  H20  absorbed  0  just  as  if  there  was  no  nitrogen  present  ; 
it  absorbed  nitrogen  just  as  if  no  0  was  present.  This  increased 
richness  in  0  is  of  vital  importance  to  fishes  (§  35).  If  the  constit- 
uent gases  were  chemically  united,  they  would  be  absorbed  by  H20 
in  the  proportion  stated  in  §  46. 

(d.)  The  gases  do  not  unite  in  any  simple  ratio  of  their  atomic 
weight.  As  will  be  seen  subsequently  (§  91),  this  is  a  very  important 
consideration. 


50  NITROGEN.  §  50 


N  ITROGEN. 

Symbol,  N  •  specific  gravity,  14 ;   atomic  weight,  14  m.  c. ; 
molecular  weight,  2S  m.  c. ;  quantivalence,  3  (or  5). 

50.  Occurrence.  —  Nitrogen  is  widely  diffused  in 
nature.    It  is  found  free  in  some  of  the  nebulas  and  in  the 
earth's  atmosphere.     In  combination,  it  exists  in  a  number 
of  minerals,  as  the  sodium  and  potassium  nitrates  (nitre) 
of  Peru  and  India.     It  also  forms  an  essential  part  of  most 
animal  and  vegetable  substances. 

51.  Preparation.  —  The  usual  way  of  preparing 
nitrogen  is  to  bum  out,  with  phosphorus,  the  oxygen  from 
a  portion  of  air  confined  over  water,  as  shown  in  Experi- 
ment 58.     Instead   of  the  burning  phosphorus,  a  jet  of 
burning  hydrogen  may  be  used.     The  nitrogen  thus  pre- 
pared is  not  perfectly  pure,  but  nearly  enough  so  for  ordi- 
nary purposes. 

(a.)  Any  method  of  getting  the  0  of  the  air  to  enter  into  com- 
bination and  form  a  compound  that  is  easily  removed  from  the 
residual  N  will  answer.  Thus,  if  a  slow  stream  of  air  be  passed 
over  bright  copper  turnings,  heated  to  redness  in  a  glass  tube, 
the  0  will  unite  with  the  copper,  leaving  the  N  to  be  collected  over 
H20. 

(&.)  Pure  N  may  be  obtained  by  chemical  processes,  such  as 
heating  ammonium  nitrite,  which  decomposes  into  H20  and  N,  as 

follows  : 

(NH4)N02=2H20  +  N2. 

52.  Physical  Properties. — Nitrogen  is  a  trans- 
parent,  colorless,  tasteless,   odorless  gas.     It  is  a  little 


54 


NITROGEN. 


51 


lighter  than  air  or  oxygen,  and  14  times  as  heavy  as  hydro- 
gen, a  liter  weighing  1.2544  g.}  or  14  criths.  It  is  very 
slightly  soluble  in  water. 


Experiment  60.— Fill  a  bell-glass 
with  0,  and  a  stoppered  bell-glass 
of  the  same  size  with  N.  Cover  their 
mouths  with  glass  plates  and  bring 
them  mouth  to  mouth,  as  shown  in 
Fig.  31.  Remove  the  stopper  and 
the  glass  plates  and  introduce  a 
lighted  taper  having  a  long  wick  (or 
a  pine  splinter).  As  the  taper  passes 
through  the  N,  the  flame  is  extin- 
guished ;  if  the  wick  be  still  glowing, 
it  will  be  rekindled  in  the  0.  By 
moving  the  taper  up  and  down  from 
one  gas  to  the  other,  it  may  be  re- 
kindled repeatedly  before  the  gases 
become  mixed  by  diffusion. 


53.  Chemical  Properties.— The  leading  charac- 
teristic of  nitrogen  is  its  inertness.     Its  properties  are 
chiefly  negative.    It  enters  into  direct  combination  with  but 
few  elements.     It  is  neither  a  combustible  nor  a  supporter 
of  combustion.     It  is  not  poisonous  ;   we  are  continually 
breathing  large  quantities  of  it.     It  kills  by  suffocation, 
by  cutting  off  the  necessary  supply  of  oxygen,  just  as 
hydrogen  or  water  does.      Its  compounds  are  generally 
unstable  and  energetic.     Some  of  them  are  decomposed 
by  being  lightly  brushed  with  a  feather  or  by  a  heavy 
step  on  the  floor  (§  113). 

54.  Uses.— The  chief  use  of  nitrogen  is  to  dilute  the 
oxygen  of  the  air  and  thus  prevent  disastrous  chemical 
activity,  especially  in  the  processes  of  respiration  and  com- 
bustion. 


52  NITROGEN.  §  55 

55.  Tests. — Nitrogen  may  be  recognized  by  its  physi- 
cal properties  and  its  refusal  to  give  any  reaction  with  any 
known  chemical  test. 

EXERCISES. 

1.  What  is  meant  by  allotropism  ?    Analysis  ?    Synthesis  ? 

2.  What  is  the  difference  between  an  elementary  and  a  compound 
molecule  ? 

3.  Why  does  the  burning  of  alcohol  yield  steam  ? 

4.  Why  does  the  gas  bottle  become  heated  in  the  preparation  of  H  ? 

5.  Whatisacrith? 

6.  Is  H  poisonous?    Can  you  live  long  in  an  atmosphere  of  H? 
Why? 

7.  Is  0  poisonous  ?    Can  you  live  long  in  an  atmosphere  of  0  ? 
Why? 

8.  Why  is  the  word  "  oxygen  "  a  misnomer  ? 

9.  Is  the  ordinary  method  of  preparing  0  analytic  or  synthetic? 

10.  What  is  the  chief  characteristic  of  0  ? 

11.  Why  is  the  inner  rather  than  the  outer  tube  of  the  compound 
blowpipe  used  for  O  ? 

12.  Name  five  constituents  of  ordinary  air. 

13.  State  five  reasons  for  holding  that  the  air  is  a  mixture. 

14.  What  is  the  weight  of  1  cu.  m.  of  N  ?    Of  0  ?  1 U  5  '} 

15.  How  many  criths  are  there  in  a  gram  ? 


SYMBOLS,    NOMENCLATURE,    MOLECULAR    AND 
ATOMIC    WEIGHTS. 


56.  Atomic  Symbols.  —  Chemists  have  a  short- 
hand way  of  writing  the  names  of  the  substances  with 
which  they  deal.     In  chemical  notation,  each  element  is 
represented  by  the  initial  letter  of  its  Latin  name.     When 
the  names  of  two  or  more  elements  begin  with  the-  same 
letter,  the  initial  letter  is  followed  by  the  first  distinctive 
letter  of  the  name.     Thus,  C  stands  for  carbon,  Ca  for 
calcium,  and  Cl  for  chlorine.     This  use  of  Latin  initials 
secures  uniformity  among  chemists  of  all  countries.     In 
only  a  few  cases  do  the  Latin  and  English  initials  differ. 
The  symbols  of  all  the  elements  will  be  found  in  Appen- 
dix 1.     These  symbols  of  the  elements  are  frequently  used 
to  represent  their  respective  substances  in  general.     Thus, 
we  speak  of  a  liter  of  0,  but  in  the  symbols  of  compound 
bodies  and  in  equations  representing  chemical  reactions 
(§  127),  the  symbol   of  an   element  represents   a  single 
atom.     To  represent  several  atoms,  we  use  figures  placed 
at  the  right  of  the  symbol  and  a  little  below  it.     Thus,  H2 
means  two  atoms  of  hydrogen.     (See  §  165,  a.) 

57.  Molecular  Symbols. — The  symbol  of  a  mole- 
cule is  formed  by  writing  together  the  symbols  of  its  con- 
stituent atoms  indicating  the  number  of  each  kind,  as  just 
stated.    A  molecule  of  water  consists  of  three  atoms,  two 


54  NOMENCLATURE.  §  57 

of  hydrogen  and  one  of  oxygen;  hence,  its  symbol  is  H20. 
Like  the  atomic  symbols  of  the  elements,  these  symbols  of 
the  molecules  of  compound  substances  are  used  to  repre- 
sent their  respective  substances  in  the  mass.  Thus,  we 
speak  of  a  liter  of  H20,  but  in  the  equations  representing 
reactions,  each  of  these  symbols  represents  a  single  mole- 
cule. To  represent  several  molecules,  we  place  the  proper 
figure  before  the  symbol.  Thus,  3H20  represents  three 
molecules  of  water,  or  six  atoms  of  hydrogen  and  three  of 
oxygen. 

Note. — The  symbol  of  a  molecule  is  sometimes  spoken  of  as  its 
formula.     Chemical  notation  is  the  written  language  of  the  science. 

58.  Nomenclature  of  the  Elements.  —  The 

nomenclature  of  chemistry  is  an  attempt  to  represent  the 
composition  of  a  substance  by  its  name.  The  names  of  the 
elements  were  generally  chosen  arbitrarily,  although  some  of 
them  allude  to  sjome  prominent  property,  as  chlorine  from 
the  Greek  cldoros,  signifying  green,  and  as  has  been  already 
stated  in  the  cases  of  hydrogen  and  oxygen.  Chemical 
nomenclature  is  the  spoken  language  of  the  science. 

59.  Nomenclature  of  Binary  Compounds.— 

The  names  of  binary  compounds  (those  containing  only  two 
elements),  have  the  characteristic  termination  -ide.  .Com- 
pounds of  single  elements  with  oxygen  are  called  oxides ; 
similar  compounds  with  chlorine  are  called  chlorides; 
those  with  sulphur  are  called  sulphides,  etc.,  etc.  Thus, 
we  have  lead  oxide,  silver  chloride  and  hydrogen  sulphide. 
When  any  two  elements  unite  in  more  than  one  proportion, 
one  or  both  of  the  words  constituting  the  name  are 
modified,  as  in  hydrogen  peroxide,  carbon  disulphide, 
mercurous  chloride  and  mercuric  chloride. 


§  60  NOMENCLATURE.  55 

6O.  Nomenclature  of  Ternary  Compounds. 

— The  most  important  compounds  containing  three  or 
more  elements  are  the  acids.  The  most  important  of 
these  consist  of  hydrogen  and  oxygen  united  to  some 
third  element,  which  is  the  characteristic  one  and  gives 
its  name  to  the  acid.  The  terminations  -ic  and  -ous 
are  used  with  the  name  of  the  characteristic  element  to 
indicate  a  greater  or  less  amount  of  oxygen  in  the  acid. 
Thus  we  have : 


Nitric  acid HN03 

Nilrow*  acid. .         ..HNO2 


Sulphuric  acid H2S04 

Sulphur0ws  acid ... .  H  2  S  0  3 


The  hydrogen  of  any  acid  may  be  replaced  with  differ- 
ent metallic  elements,  giving  us  the  large  and  important 
class  of  compounds  called  salts.  The  generic  name  of  the 
salt  is  formed  by  changing  the  -ic  termination  of  the 
name  of  the  acid  to  -ate,  or  by  similarly  changing  -ous 
to  -ite.  Thus,  phosphor^  acid  furnishes  "phosphates, 
while  phosphorous  acid  furnishes  phosphite*.  The  specific 
name  of  the  salt  is  derived  from  that  of  the  element  used 
to  replace  the  hydrogen  of  the  acid.  Thus  we  have  : 


Nitric  acid HN03 

Nitrous  acid. .         ..HN00 


Potassium  nitrate  —  KN03 
Potassium  nitrite KN02 


Sulphuric  acid H3S04  !  Potassium  sulphate. K2S04 

Sulphurows  acid H3S03  !  Potassium  sulphite..  K2S68 

(a.}  Some  chemists  prefer  to  modify  the  name  of  the  replacing 
element  making  it  an  adjective,  e-  g.,  potassic  nitrate.  In  the  case 
of  English  words  that  can  not  be  adapted  to  such  adjective  forms, 
the  Latin  word  is  used;  e.  g.,  plumbic  nitrate  for  lead  nitrate.  In 
some  cases  old  forms  are  still  frequently  used  ;  e.g.,  chlorate  of  pot- 
ash for  potassium  chlorate,  or  protosulphate  of  iron  for  ferrous  sul- 
phate. In  some  cases,  a  strict  adherence  to  systematic  chemical 
nomenclature  would  lead  to  the  use  of  inconvenient  names,  as  potas- 
sium aluminum  sulphate  for  common  alum.  In  the  so-called  organic 
compounds  this  inconvenience  would  frequently  be  very  marked. 


56  THE  MICROCRITH.  §  6 1 

61.  Ampere's  Law. — The  corner-stone  of  modern 
chemistry, "as  distinguished  from  the  chemistry  of  the  last 
generation,  is  a  proposition  known  as  Ampere's  or  Avoga- 
dro's  law,  the  evidence  in  support  of  which  can  not  be 
satisfactorily  presented  in  this  place.     It  may  be  stated  as 
follows  :  Equal  volumes  of  all  substances  in  the  gas- 
eous condition,  the  temperature  and  pressure  being 
the  same,  contain  the  same  number  of  molecules, 

62.  The  Microcrith.— A  liter  of  hydrogen  weighs 
.0896  #.,  or  one  crith.     It  has  been  estimated  that  a  liter 
of  hydrogen,  or  of  any  other  gas,  contains  1024  molecules. 
Then  each  molecule  o'f  hydrogen  weighs  ^^  crith s,  and 
each  hydrogen  half-molecule  weighs  ^ritF*  crith  s.     The 
weight  of  the  hydrogen  half-molecule  has  been  called  a 
microcrith  (m.  c.),  and  the  term  is  so  convenient  that  we 
shall  use  it.     It  must  be  remembered  that  the  absolute 
value  of  a  m.  c.  is,  as  yet,  unknown,  because  the  number 
1034,  used  above,  is  only  an  "estimate."    When  physicists 
determine  accurately  the  number  of  molecules  in  a  given 
volume  of  a  gas,  the  chemist  will  know  the  absolute  value 
of  a  m.  c.     It  will  answer  all  of  our  present  purposes  to 
remember  that  umicrocrith  is  the  weight  of  one  atom 
of  hydrogen,  and  that  it  is  a  real  unit,  measuring 
a  definite  quantity  of  matter,  for,  as  we  shall  soon  see, 
the  hydrogen  half-molecule  is  a  hydrogen  atom  (§174). 

63.  Molecular  Weights.— The  hydrogen  molecule 
weighs  2  m.  c.     Knowing  that  oxygen  is  sixteen  times  as 
heavy  as  hydrogen  and  remembering  Ampere's  law,  it  is 
evident  that  the  oxygen  molecule  must  weigh  32  m.  c. 
Similarly,  we  see  that  the  nitrogen  molecule  weighs  28  m.  c., 
etc.    In  brief,  the  molecular  weight  (in  microcriths) 


§64 


ATOMIC    WEIGHTS. 


of  a  substance  is  twice  the  specific  gravity  (hydrogen 
standard)  of  the  substance  in  the  aeriform  condi- 
tion. Dry  steam  being  nine  times  as  heavy  as  hydrogen, 
its  molecular  weight  is  18  m.  c.  At  the  same  time,  the 
molecular  weight  must  equal  the  sum  of  the  weights  of 
the  atoms  in  the  molecule.  The  combining  weight  of 
a  chemical  compound  is  its  molecular  weight. 

(a.)  The  only  known  method  for  determining  the  molecular  weight 
of  a  compound  with  certainty  is  the  determination  of  its  vapor 
density.  The  molecular  weight  of  a  compound  that  is  not  volatile, 
or  volatile  only  at  a  temperature  so  high  as  to  prevent  the  determina- 
tion of  its  vapor  density,  or  that  is  not  volatile  without  decomposi- 
tion, must  be  considered  as  unknown  or,  at  least,  doubtful. 

64.  Atomic  Weights. — The  chemist  is  able  to 
analyze  any  known  compound,  and  to  determine  the  exact 
proportion  of  the  elements  constituting  it.  We  have 
already  seen  how  he  determines  the  molecular  weights. 
One  method  of  determining  the  atomic  weights  will  be 
best  understood  from  an  example. 

(a).  Suppose  the  chemist  wishes  to  determine  the  atomic  weight  of 
O.  He  begins  with  steam  and  finds,  from  its  specific  gravity,  that  its 
molecular  weight  is  18  m.  c.,  and,  by  analysis,  that  f  of  this  is  0.  He 
proceeds  in  this  way  with  all  of  the  gaseous  or  volatile  compounds 
of  0,  and  tabulates  some  of  the  results,  as  follows : 


SUBSTANCES. 

WEIGHT  OF 
MOLECULE. 

WEIGHT  OP  O  IN  MOLE- 
CULE. 

Water 

H20 
CO 
NO 
C,H60 
<C,cH»)0 

sNo°,' 

C,H4O, 

so, 

(CH,V(BO, 
(C,Hs),BOi 
(C,H.)ASi04 

OsO, 

03 

18  m.  c. 
28 
30 
46 
74 
44 
46 
64 
60 
80 
104 
146 
208 
263 

32      " 

16  m.  c. 
16     ' 
16     ' 
16     l 
16     ' 
32     ' 
32     ' 
32     ' 
32    " 
48    " 
48    " 
48    " 
64    " 
64    " 

32    " 

16  m.  c.  x  1. 

u 

16  m.  c.  x  2. 

« 
16  m.  c.  x  3. 

16  m.  c.  x  4. 
16  m.  c.  x  2. 

Carbon  monoxide  
Nitric  oxide  

Alcohol        .  . 

Ether 

Carbon  dioxide  
Nitrogen  peroxide  
Sulphur  dioxide.  ....  . 
Acetic  acid 

Sulphur  trioxide  
Methyl  borate  
Ethyl  borate  
JEthvl  silicate    .        ... 

Osmium  oxide 

Me.,  etc. 
Oxygen  

58  ATOMIC   WEIGHTS.  §  64 

He  notices  that  the  smallest  weight  of  0  in  any  of  these  com- 
pounds is  16  m.  c.,  and  that  all  the  others  are  simple  multiples  of 
this.  lie  cannot  believe  that  this  is  mere  chance,  especially  as  he  finds 
similar  results  in  determining  other  atomic  weights.  The  only  ex- 
planation possible  is  that  this  10  m.  c.  is  the  weight  of  a  definite 
quantity  of  0,  and  that  it  represents  the  least  quantity  of  0  that  can 
enter  into  combination  (§  5).  Hence,  16  m.  c.  is  the  atomic  weight  of 
0,  and  the  substances  analyzed  contain  respectively  one,  two,  three 
and  four  atoms  of  0  to  the  molecule.  Of  course,  the  symbols  in  the 
second  column  of  the  table  above  can  not  be  determined  until  after 
the  determination  of  the  atomic  weights  of  the  elements  involved. 
The  table  also  shows  that  the  0  molecule  consists  of  two  atoms. 
The  combining  weight  of  an  element  is  its  atomic  weight. 

65.  Composition  of  Elementary  Molecules. 

— Chemists  have  ascertained  that  hydrogen,  oxygen,  nitro- 
gen, chlorine,  bromine,  iodine,  sulphur,  selenium,  tellu- 
rium and  potassium  have  two  atoms  to  the  molecule  ;  that 
cadmium  and  mercury  have  one,  and  that  phosphorus  and 
arsenic  have  four.  Nothing  is  yet  known  concerning  the 
composition  of  the  other  elementary  molecules.  When 
the  specific  gravity  of  the  vapor  of  any  of  the  other  ele- 
ments is  accurately  determined,  the  molecular  weight  of 
that  element  becomes  a  matter  of  knowledge  (§  63). 
Then,  knowing  both  the  molecular  and  the  atomic  weight, 
the  composition  of  the  molecule  is  at  once  removed  from 
the  region  of  hypothesis  to  that  of  fact. 

EXEKCISES. 

1.  Which  will,  under  similar  conditions,  occupy  the  more  space, 
100  molecules  of  H  or  100  molecules  of  N  ? 

2.  (a.)  From  what  acid  may  we  consider  that  sodium  sulphate  is 
formed  ?    (&.)  Sodium  sulphite  ? 

3.  (rt.)  Write  the  symbol  for  hydrogen  monoxide.    (&.)  For  hydro 
gen  dioxide. 

4.  What  is  the  molecular  weight  of  a  vapor  that  is  23  times  as 
heavy  as  H  ?  i[t 

5.  How  many  microcriths  are  there  in  a  gram  ? 


COMPOUNDS    OF    HYDROGEN,    OXYGEN    AND 
NITROGEN. 


ECTfON  1. 


AMMONIA. 

66.  Occurrence. — Ammonia  (NH3)  exists  in  small 
quantities  in  the  air,  whence  it  is  brought  down  to  the. 
earth  by  rain  and  dew.    It  is  formed  by  the  putrefaction 
of  animal  and  vegetable  matter.     The  ammonia  of  com- 
merce is  chiefly  obtained  from  ammoniacal  salts  incident- 
ally produced  in  the  manufacture  of  coal  gas.      Ammonia 
is  familiar  to  many  under  the  name  of  hartshorn. 

67.  Preparation.  —  The 

preparation  of  ammonia  is 
sufficiently  illustrated  by  the 
next  three  experiments. 


Experiment  61. — Into  a  half  liter 
flask,  pour  about  200  cu.  cm.  of  strong 
ammonia  water  (N  H  4  H  0).  Close  the 
flask,  a,  with  a  cork  carrying  a  fun- 
nel tube  and  a  delivery  tube,  as 
shown  in  Fig.  32.  The  delivery  tube 
should  pass  to  the  bottom  of  a  tall 
drying  bottle,  6,  containing  about  a 
liter  of  quicklime  broken  into  small 
pieces.  Gently  heat  the  liquid  in  a, 


FIG.  32. 


60 


AMMONIA. 


§67 


and  N  H  3  (which  is  a  gas)  will  be  given  off.  After  passing  through  b 
it  may  be  collected  by  upward  displacement  or  over  mercury.  If 
collected  over  mercury,  the  funnel  tube  in  a  must  have  a  consider- 
able length. 

Experiment  62. — In  a  mortar,  or  the  palm  of  the  hand,  rub  together 
equal  weights  of  pulverized  ammonium  chloride  (sal-ammoniac, 
NH4CI)  and  quicklime (CaO).  Notice  the  smell  before  and  after  rub- 
bing. 

2NH4CI  +  CaO  =  CaCL,  +  H20  +  2NH3. 

Experiment  G3. — Mix  25  or  30  g.  of  pulverized  ammonium  chloride 
with  50  to  60  g.  of  freshly  slaked  lime  (CaO  +  H20  =  CaH202), 
that  has  been  allowed  to  cool.  Place  the  mixture  in  a  half  liter  flask 
and  add  enough  H20  to  cause  it  to  aggregate  in  lumps  when  stirred 
with  a  rod.  When  the  mixture  is  gently  heated,  NH3  is  produced 
in  accordance  with  the  reaction, 

2NH4CI  -hCaH.O.,  =  CaCI2  +  2H30  +  2NH3. 

The  gas,  after  being  dried,  may  be  collected  in  bottles  by  upward 
displacement  and  the  bottles  corked.  This  is  the  most  common  way 
of  preparing  NH3  in  the  laboratory. 

Experiment  64.—  Fill  a  liter  bottle,  «,  with  NH3 
by  upward  displacement.  By  holding  at  the 
mouth  of  the  inverted  bottle  a  moistened  strip  of 
turmeric  paper  or  red  litmus 'paper,  the  experi- 
menter will  be  able  to  tell  when  the  bottle  is 
filled  ;  the  turmeric  will  turn  brown  or  the  litmus 
blue.  Close  the  bottle  with  a  cork  (a  rubber 
stopper  is  preferable)  through  which  passes  a 
small  glass  tube.  Place  the  end  of  this  tube  in 
H20,  colored  with  red  litmus  solution  (App.  24). 
The  H2O  will,  in  a  moment,  rush  into  the  bottle 
with  violence,  changing  from  red  to  blue  as  it 
enters  (see  Exp.  106). 

FIG.  33.  Experiment  65.  —  From  the  flask  of  Experi- 

ment 63,  pass  the  gas  through  a  series  of  Woulffe 
bottles,  partly  filled  with  H20,  as  shown  in  Fig.  34.  The  delivery 
tube  of  one  bottle  terminates  under  H20  in  the  next.  A  safety 
tube,  s,  (open  at  both  ends)  passes  through  the  cork  in  the  middle 
neck  of  each  bottle.  The  delivery  tube  of  the  generating  flask 
should  not  dip  into  the  H30  of  the  first  bottle.  This  precaution 
prevents  the  possibility  of  H20  being  forced  back  into  the  heated 


§68 


AMMONIA. 


61 


FIG.  34. 

flask  and  breaking  it.  It  is  well  to  keep  the  Woulffe  bottles  in 
vessels  containing  cold  H2O,  as  heat  is  evolved  in  the  condensation 
of  the  NH3.  At  the  end  of  the  experiment,  put  the  ammonia  water 
just  prepared  into  convenient  bottles,  cork  tightly,  and  save  for 
future  use. 

68.  Physical  Properties. — Ammonia  is  a  color- 
less, irrespirable  gas  and  has  a  pungent  odor.  It  is  much 
lighter  than  air,  its  specific  gravity  being  8$,  i.  e.,  a  liter 
of  it  weighs  8.5  criths  (.7616  #.).  It  liquefies  under  a 
pressure  of  6£  atmospheres  at  10°C.,  4J  atmospheres 
at  0°C.,  or  1  atmosphere  at  —  40°C.  The  liquid  solidifies 
at  —  75°C.  Under  ordinary  conditions,  the  liquid  rapidly 
evaporates,  producing  intense  cold  (Ph.,  §  526).  It  is  re- 
markably soluble  in  water,  one  volume  of  which  absorbs 
803  volumes  of  the  gas  at  14°C., 
or  1148  at  0°C.  This  saturated 
solution  (aqua  ammonia)  has 
a  specific  gravity  of  .85. 

Experiment  66.  —  From  a  gas 
holder  containing  five  volumes  of  H 
and  two  volumes  of  nitric  oxide 
(NO,  §  83),  pass  a  stream  of  the  mixed  pIG 

gases  through  a  bulb  tube  contain- 


AMMONIA. 


§69 


ing  platinized  asbestos,  as  indicated  in  Fig.  35.  The  gases  escap- 
ing at  a  will  redden  moistened  blue  litmus  paper.  Heat  the  bulb  ; 
the  H  and  N  combine,  NH3  is  formed,  and,  as  it  escapes  at  a,  turns 
the  reddened  paper  blue  again. 

Experiment  67.  —  From  the  drying-bottle  of  Experi- 
ment 61,  lead  the  delivery  tube,  d,  through  a  narrow 
glass  cylinder  to  its  upper  end,  as  shown  in  Fig.  36. 
As  the  NH3  issues  at  a,  try  to  light  it ;  it  will  refuse  to 
burn.  Through  the  flexible  tube,  &,  pass  a  current  of 
O  into  the  cylinder.  The  jet  of  NH3  being  now  sur- 
rounded by  an  atmosphere  of  0,  may  be  lighted ;  it 
will  burn  with  a  yellowish  flame. 

Experiment  68.— Pass  a  stream  of  0  from  the  gas 
holder  through  a  strong  aqueous  solution  of  NH3  in  a 
flask.  Heat  the  flask  and  bring  a  flame  into  contact 
with  the  mixed  gases  as  they  issue  from  the  neck  of 
ths  flask.  They  will  burn  with  a  large  yellow  flame. 


FIG.  36. 


Experiment  69— Upon  a  piece  of  broadcloth  or  dark  colored  calico, 
let  fall  a  few  drops  of  dilute  sulphuric  acid.  The  acid  will  produce 
red  spots.  Apply  ammonia  water  to  the  spots  and  they  will  disap- 
pear. This  is  a  familiar  experiment  in  most  laboratories. 

69.  Chemical  Properties.  —  Ammonia  and  its 
aqueous  solution  have  -strong  alkaline  properties  (§1G8), 
neutralizing  acids  and  restoring  vegetable  colors  changed 
by  acids.     The  gas  is  combustible  only  when  mixed  with 
oxygen. 

70.  Composition.  —  Analysis  of  ammonia  shows 
that  it  is  composed  of  fourteen  weights  of  nitrogen  to  three 
weights  of  hydrogen,  or  of  one  volume  of  nitrogen  to 
three  of  hydrogen,  the  four  volumes  of  the  constituents 
being  condensed  to  two  volumes  of  the  compound.     This 
may  be  represented  to  the  eye  as  follows : 


1  m.  c, 


14  m.c. 


3,17 


§  71  AMMONIA.  63 

In  other  words,  when  ammonia  gas  is  decomposed,  it 
doubles  its  volume,  yielding  half  its  volume  of  nitrogen, 

and  one  and  a  half  times  its  volume  of  hydrogen. 

• 

(a.)  Suppose  100  cu.  cm.  of  NH3  to  be  confined  over  mercury  in  a 
eudiometer.  By  producing  electric  sparks  in  it,  the  gas  is  decom- 
posed and  increases  its  volume  to  200  cu.  cm.  Add,  say  100  cu.  cm. 
of  0  and  produce  a  spark  in  the  mixed  gases.  There  is  a  shrinkage 
of  225  cu.  cm.,  the  gases  now  measuring  75  cu.  cm.  The  shrinkage 
was?  due,  of  course,  to  the  formation  of  H20  Hence, two- thirds  of 
the  225  cu.  cm.,  or  150  cu.  cm.,  was  H,  and  the  other  75  cu.  cm.  was  0. 
But,  as  we  introduced  100  cu.  cm.  of  0,  and  only  75  cu.  cm.  of  it 
has  combined,  the  other  25  cu.  cm.  must  be  in  the  eudiometer  as 
part  of  the  residual  75  cu.  cm.  Consequently,  we  have  left  50  cu.  cm. 
of  N,  and  25  cu.  cm.  of  0.  The  50  cu.  cm.  of  N  and  tlie  150  cu.  cm. 
of  H  came  from  the  100  cu.  cm.  of  NH3. 

71.  Uses.  —  Ammonia  water  is  largely  used  in  the 
laboratory  and  as  a  detergent.  It  is  also  largely  used  in 
the  preparation  of  sodium  carbonate,  in  the  production 
of  aniline  colors  and  in  the  manufacture  of  indigo.  Liquid 
ammonia  is  used  in  the  freezing  of  artificial  ice. 

Experiment  70.—  Prepare  100  cu.  cm.  of  the  "  Nessler  re-agent," 
as  follows:  into  80  cu.  cm.  of  H20  put  3.5  g.  of  potassium  iodide, 
and  1.3  g.  of  mercuric  chloride  (corrosive  sublimate,  HgCI2,  a  deadly 
poison).  Heat  to  the  boiling  point  and  stir  until  the  solids  are  dis- 
solved. Add  a  saturated  solution  of  HgCl^in  H20,  drop  by  drop, 
until  the  color  of  the  red  mercuric  iodide  is  just  perceptibly  per- 
manent. Then  add  16  g.  of  potassium  hydrate  (caustic  potash), 
or  12  g.  of  sodium  hydrate  (caustic  soda),  and  add  H20  until  the 
solution  measures  100  cu.  cm.  The  reagent  should  be  of  a  slightly 
yellowish  tint.  If  it  be  colorless,  add  a  little  more  of  the  HgCI2 
solution,  until  the  permanent  tint  is  just  perceptible.  Place  the 
liquid  in  a  well-stoppered  bottle. 

Drop  about  2  cu.  cm.  of  the  Nessler  reagent  into  50  cu.  cm.  of  a 
very  weak  solution  of  NH3  and  stir  the  mixture,  which  will  be 
changed  to  a  brown  color;  the  more  NH3  in  the  solution,  the 
deeper  the  brown.  Save  the  rest  of  the  reagent  in  carefully  stoppered 
bottles. 


64  AMMONIA.  §  72 

72.  Tests. — The  tests  for  ammonia  are  its  pungent 
odor,  its  turning  moistened  red  litmus  paper  blue,  the 
fumes  of  ammonium  chloride  it  produces  with  hydro- 
chloric acid  (Exp.  6),  and  the  test  with  the  Nessler 
reagent.  The  ammonia  of  ammoniacal  compounds  may  be 
generally  set  free  by  heating  the  compound  with  potas- 
sium hydrate  and  then  detected  by  the  above  means. 
Ammonia  tests  play  an  important  part  in  the  analysis  of 
potable  waters — the  development  of  ammonia  indicating 
contamination  by  organic  matter. 

EXERCISES. 

1.  (a.)  What  weight  of  H  is  contained  in  17 g.  of  NH3  ?    (ft.)  What 
volume  of  H?  ,i|^( 

2.  (a.)  What  volume  of  H  can  be  produced  by  the  decomposition 

of  2  I.  of  N H 3  ?    (&.)  What  weight  of  H  ?  I  - r^ 

3.  («.)  What  weight  of  H  can  be  united  with  28  g.  of  N  to  form 
ammonia  ?    (&.)  What  volume  of  H  ?  4  C  i  & 

4.  (a.)  What  weight  of  N  can  be  united  with  9  g.  of  H  to  form  N  H , ': 
(&.)  What  will  be  the  weight  of  the  product  V 

5.  (a.)  If    100  cu.  cm.  of  NH3    be  decomposed  in  a   eudiometer, 
100  cu.  cm.  of  0  added,  and  an   electric  spark  passed  through  the 
mixed  gases,  what  gases  will  remain  ?    (&.)  What  will  be  the  volume 
of  each? 

6.  Why  were  the  safety  tubes  used  in  Exp.  65  ? 


§74 


X1TRIC  ACID. 


65 


N  ITRIC    ACI  D. 

73.  Sources.  —  The  chief    sources  of   nitric  acid, 
(aqua  fortis,  HN03,)  are  potassium  nitrate  (saltpetre  or 
nitre,)  which  is  obtained  in  abundance  in  India,  and  so- 
dium nitrate  (Chili  saltpetre  or  soda  nitre),  which  is  found 
as  an  efflorescence  on  the  soil  of  a  sterile  region  in  Chili 
and  Peru,  and  exported  in  large  quantities  from  those 
countries. 

74.  Preparation. — Nitric  acid  is  always  prepared 
from  a  nitrate  by  distillation  with  sulphuric  acid  (H2S04). 

(a.)  Into  a  quarter  liter  retort,  a,  having  a  glass  stopper,  put  50  g. 
of  pulverized  potassium  nitrate  (KN03>)  or  40  g.  of  pulverized  sodium 
nitrate  (NaN03,)  and  35  cu.  cm.  of-  strong  H8S04.  The  mate- 
rials should  be  introduced  through  the  tubulure,  8,  and  care  taken 
that  none  falls  into  the  neck  of  the  retort.  It  is  well  to  use  a  paper 
funnel  for  the  nitrate  and  a  funnel  tube  for  the  acid.  Replace  the 
stopper  and  place  the  retort  upon  sand  in  a  shallow  sheet  iron  or 
pressed  tin  pan,  supported  by  a  ring  of  the  retort  stand  over  the  lamp, 
or  upon  wire  gauze,  as  shown  in  the  figure.  The  use  of  the  "  sand 
bath  "  or  gauze  lessens 
the  danger  of  breaking 
the  retort.  Place  the 
neck  of  the  retort  loose- 
ly in  the  mouth  of  a 
Florence  flask,  r,  or 
other  convenient  re- 
ceiver, kept  cool  by 
H80.  It  is  well  to  cover 
the  receiver  with  cloth 
or  bibulous  paper  ;  the 
H20  may  be  brought 
by  a  rubber  tube  siphon  „ 

(Ph.,  §  298)  from  a  pail 
of  H,0   sufficiently  elevated.     As  the  retort  is  heated,  the  nitrate 


66  NITRIC  ACID.  §  74 

liquefies,  reddish  fumes  appear,  and  HN03  condenses  in  the  neck  of 
the  retort  andjn  the  receiver.  The  fumes  in  the  retort  will  soon  dis- 
appear ;  continue  the  distillation  until  they  reappear. 


Transfer  the  HN03  to  a  glass  stoppered  bottle  and  save  it  for  future 
use.  After  the  retort  has  become  thoroughly  cool,  the  solid  residue, 
acid  potassium  sulphate,  should  be  dissolved  by  heating  with  H20, 
and  then  removed. 

(&.)  In  the  arts,  the  retort  is  made  of  cast  iron  and  the  distillate  is 
condensed  in  earthenware  receivers.  A  higher  temperature  and 
frequently  only  half  as  much  H2S04  are  used. 

2KN03  +  H2S04  =  K0S04  +  2HN03) 
2NaN03  +  HaS04  =  N~a2S04  +  2HN03. 

75.  Physical  Properties. — Nitric  acid  is  a  fuming 
liquid,  colorless  when  pure,  but  generally  slightly  tinted 
with  the  fumes  seen  in  the  retort  during  its  preparation. 
It  has  a  specific  gravity  of  1.52,  freezes  aW>5°C.,  and  boils 
with  partial  decomposition  at  86°C.     It  may  be  mixed 
with  water  in  all  proportions,  the  aqua  fortis  of  commerce 
containing  from  40  to  60  per  cent,  of  nitric  acid. 

Experiment  71. — Pulverize  a  few  grams  of  charcoal  and  heat  it. 
Upon  the  heated  charcoal,  pour  a  little  strong  HN03.  The  charcoal 
is  rapidly  oxidized  to  combustion. 

Experiment  7%. — From  the  end  of  a  meter  stick,  drop  a  thin  slice 
of  phosphorus  into  strong  HN03.  The  phosphorus  is  oxydized  to 
violent  combustion. 

Experiment  73. — Into  dilute  HN03,  dip  a  skein  of  white  sewing 
silk.  In  a  few  minutes,  remove  and  wash  it  thoroughly  with  H20. 
The  silk  will  be  permanently  colored  yellow. 

Experiment  74- — Put  a  sheet  of  if  Dutch  leaf,"  which  may  be  ob- 
tained of  a  sign  painter,  into  a  test  tube  and  pour  upon  it  a  small 
quantity  of  HN03.  The  metal  is  instantly  dissolved. 

76.  Chemical  Properties. — Nitric  acid  is  a  power- 
ful oxidizing  agent,  and  one  of  the  most  corrosive  known 
substances.    It  colors  nitrogenous  animal  substances  (e.  g., 


§  7$  XITRIC  ACID.  67 

silk,  skin  and  parchment)  yellow,  and  converts  many 
non-nitrogenous  substances  (e.  g.,  cotton  and  glycerine) 
into  violently  explosive  compounds.  It  dissolves  all  of 
the  common  metals  except  gold  and  platinum,  forming 
nitrates. 

Experiment  75. — Cover  a  smooth  piece  of  brass  or  copper  with  a 
film  of  beeswax.  With  a  sharp  instrument,  write  your  name  upon 
the  metal,  being  sure  to  cut  through  the  wax.  Cover  the  writing 
with  strong  HN03,  In  a  few  moments,  the  name  will  appear  in  a 
tracery  of  minute  bubbles.  A  few  moments  later,  wash  the  acid 
away  with  H30  and  remove  the  wax.  The  autograph  will  be  etched 
upon  the  metal. 

/ 

77.  Uses. — Nitric  acid  is  largely  used  in  the  laboratory 
and  in  the  arts,  in  the  manufacture  of  gun  cotton,  nitro- 
glycerin,  etc.,  and  in  the  preparation  of  aqua  regia  (§  114). 
Engravers  use  it  for  etching  on  copper  and  steel. 

Experiment  76. — Into  a  test  tube,  put  a  few  bits  of  copper  and 
cover  them  with  HN03.  The  red  fumes  of  nitric  oxide  appear,  and 
the  liquid  is  colored  blue  by  the  copper  nitrate  formed. 

Experiment  77. — Into  a  test  tube,  put  a  few  cu.  cm.  of  a  dilute  so- 
lution of  mdigo.  Add  HN03  until  the  blue  solution  is  bleached. 

78.  Tests.— In  testing  for  nitric  acid,  first  try  blue 
litmus  paper.     If  this  test  paper  besnot  reddened  when 
dipped  into  the  liquid  in  question,  the  liquid  is  not  an 
acid.     If  it  be  reddened,  the  liquid  is  some  acid.     As  the 
nitrates  are  all  easily  soluble,  tests  for  nitric  acid  yield  no 
precipitates.      Free  nitric  acid  may  be  detected  by  its 
bleaching  an  indigo  solution,  or  by  its  forming  red  fumes 
when  added  to  copper  bits  or  filings.     Nitrates  show  the 
same  effects  when  heated  with  sulphuric  acid,  because  of 
the  nitric  acid  thus  set  free.     The  nitrates  also  deflagrate 
when  thrown  upon  burning  charcoal. 


68 


NlTBOOEX   OXIDES. 


§79 


N  ITROGEN    OXIDES. 

Experiment  78. — In  a  small  evaporating  dish  (App.  21),  place  a  few 
cu.  cm.  of  HN03  and  add  an  equal  bulk  of  H20.  In  another  vessel, 
place  a  small  quantity  of  NH4HO  similarly  diluted.  Into  the  first 
liquid,  dip  a  strip  of  blue  litmus  paper.  The  change  of  color 
shows  an  acid.  Dip  this  litmus  paper  (now  red)  into  the  other  liquid. 
The  restoration  of  the  blue  color  shows  the  presence  of  an  alkali. 
To  the  first  liquid,  add  the  second,  in  small  quantities  at  first,  and 
finally  drop  by  drop.  Stir  the  mixture  continually  with  a  glass  rod, 
and  test  with  blue  litmus  paper  after  each  addition  of  NH4HO. 
At  last,  it  will  be  found  that  the  mixture  will  neither  redden  blue 
litmus  papor  nor  restore  red  litmus  paper  to  its  original  blue.  It  has 
neither  an  acid  nor  an  alkaline  reaction.  The  acid  has  been  "  neu- 
tralized "  by  the  alkali,  and  we  have  a  solution  of  a  neutral  salt. 
Without  boiling  the  liquid,  evaporate  it  until,  when  the  glass  rod  is 
removed,  the  adhering  liquid  becomes  almost  solid  upon  cooling:. 
Crystals  will  now  form  upon  the  cooling  of  the  liquid  ;  these  crystals 
are  to  be  carefully  drained  and  dried.  They  are  ammonium  nitrate 
(NH4NO,). 

79.  Nitrogen  Monoxide.  —  Nitrogen  monoxide 
(nitrogen  protoxide,  nitrous  oxide,,  laughing  gas,  N20,)  is 
prepared  by  decomposing  ammonium  nitrate  by  heat. 

(a.)    Into  a  small   Florence    flask,  /,   place    a  tablespoonful    of 

N  H  4  N  0  3 .  Heat  gently  and  carefully 
over  the  sand  bath  or  a  piece  of  wire 
gauze,  and  collect  the  gas  over  warm 


NH4N08  =  N20  +  2H30. 

To  show  that  H30  is  produced,  in- 
terpose, between  the  Florence  flask 
and  the  water  pan,  a  condensing  bot- 
tle placed  in  ice  water,  as  shown  at  c, 
in  Fig.  38.  Test  the  liquid  that  col- 
lects in  this  bottle  by  dropping  a 
small  piece  of  potassium  into  it.  The 


FIG.  38. 


§  82  XITROGKX    OXIDES.  69 

flask  would  break  before  all  of  the  NH^NO-j  was  decomposed,  but  by 
heating  a  small  quantity  of  the  nitrate  upon  platinum  foil,  it  will  be 
seen  that  no  residue  is  left. 

Experiment  79. — Repeat  Exps.  33,  36,  and  37,  using  N20  instead  of 
0.  (These  are  simply  combustions  in  0,  the  N20  being  decomposed 
into  its  elements.) 

80.  Properties. — Nitrogen  monoxide  is  a  colorless, 
sweet  tasting  gas,  and  a  good  supporter  of  combustion. 
One  liter  of  it  weighs  22  criths.     It  may  be  liquefied  and 

'solidified  by  cold  and  pressure.  When  the  liquid  is  mixed 
with  carbon  disulphide  and  evaporated  in  a  vacuum,  it  pro- 
duces the  remarkably '  low  temperature  of  — 140°  C. 
(Ph.,  §  526).  It  is  largely  soluble  in  alcohol  or  water,  but 
less  so  in  warm  water.  When  pure  and  mixed  with  one- 
fourth  its  volume  of  oxygen,  it  may  be  safely  inhaled,  pro- 
ducing the  effects  that  have  secured  for  it  the  name  of 
laughing  gas.  If  its  inhalation  is  continued,  it  acts  as  an 
anaesthetic. 

81.  Composition.  —  The   composition  of  nitrogen 
monoxide  is  strictly  analogous  to  that  of  steam  (Exp.  53), 
two  volumes  of  nitrogen  uniting  with  one  of  oxygen  to 
form  two  of  this  compound. 


14  m.c. 


O 

16  m.c. 


44  m.  c. 


When  decomposed  by  electric  sparks,  it  yields  1  £  times 
its  own  volume  of  mixed  gases,  as  represented  by  the 
typical  squares  above. 

82.  Ilypoiiitrous  Acid.— This  acid  (H NO)  has  not  yet  been 
prepared,  but  the  corresponding  salt,  potassium  hyponitrite  (KNO),  is 
known.  We  may  imagine  this  reaction  :  NgO  -f  H20  =  2HNO. 


70 


NITROGEN  OXIDES. 


§83 


83.  Mtric  Oxide.— Nitric  oxide  (nitrosyl,  NO,)  is 
prepared  by  the  action  of  dilute  nitric  acid  upon  copper 
clippings,  turnings  or  filings.     The  gas  may  be  collected 
over  water.     The  apparatus  is  arranged  as  shown  in  Fig.  6. 
The  generating  bottle  is,  at  first,  filled  with  red  fumes 
(§  87)  but  the  gas  collected  over  water  is  colorless.    Save 
the  blue  solution  of  copper  nitrate  [Cu(N03)2]- 

3Cu  -f  8HN03  =  3NO  +  3Cu  (N03)2  +  4H20. 

Experiment  80, — Into  a  bottle  of  NO,  lower  a  burning  splinter, 
a  burning  candle,  or  sulphur  burning  in  a  deflagrating  spoon 
(App.  19).  It  will  not  burn  in  the  gas. 

Experiment  81. — Into  a  bottle  of  NO,  lower  a  deflagrating  spoon 
containing  a  bit  of  vigorously  burning  phosphorus,  the  size  of  a  pea. 
It  will  continue  to  burn  with  great  brilliancy. 

Experiment  82. — In  a  jar  of  NO,  place  a  few  drops  of  carbon  di- 
sulphide.  Close  the  bottle  for  a  few 
minutes  to  allow  the  liquid  to  evapo- 
rate and  its  vapor  to  mix  with  the  NO. 
In  a  dark  room,  bring  a  lighted  taper  to 
the  open  mouth  of  the  jar,  as  shown  in 
Fig.  39.  The  mixture  burns  with  a  vivid 
light  rich  in  actinic  rays  (Ph.,  §  651). 

Experiment  83. — Into  a  jar  of  NO, 
standing  in  the  water  pan,  pass  a  stream 
of  0  from  the  gas  holder.  After  the 
red  fumes,  that  are  promptly  formed 
have  been  dissolved  by  the  H80,  re- 
peat the  experiment  several  times,  notic- 
ing the  phenomena  carefully. 
FIG.  39. 

Experiment  84. — Fill  a  large  bell  glass  with  NO  at  the  water  bath. 
Cover  the  mouth  under  H20  with  a  glass  plate,. invert  the  bell  glass 
and  remove  the  plate  (Fig.  40).  The  NO  absorbs  0  from  the  air  and 
forms  a  cloud  of  the  now  familiar  red  fumes  (Exp.  45). 

84.  Properties.  —  The  leading  property  of   nitric 
oxide  is  its  strong  attraction  for  oxygen.     Its  relation  to 


§87 


NITROGEN  OXIDES. 


combustion  is  peculiar.     Ordinary  combustibles  will  not 
burn  in  it  at  all ;  phosphorus  may  be      jfo 
melted  in  the  gas  without  kindling, 
but  when  once  well  aflame  it  burns 
with  great  energy.     The  gas  is  color- 
less  and  slightly  soluble  in  water. 
One  liter  of  it  weighs  15  criths. 

85.  Composition.  —  This  is 
the  first  compound  that  we  have 
studied,  the  gaseous  constituents  of 
which  unite  without  condensation. 
One  volume  of  oxygen  unites  with 
one  volume  of  nitrogen  to  form  two 
volumes  of  nitric  oxide. 


FIG.  40. 


86.  Nitrogen    Trioxicle.  —  This  gas  (nitrous    anhydride, 
N203,)  is  an  obscure  compound  that  unites  with  water  to  form  nitrous 
acid(HN02). 

N203  +  H20  =  2HN02. 

87.  Nitrogen  Peroxide.  —  Nitrogen  peroxide  (ni- 
tryl,  NO 2,)  is  the  brownish  red  gas  with  which  we  have  so 
frequently  met  in  our  experiments  with  nitric  acid  and  the 
nitrogen  oxides.     It  is  best  prepared  by  bringing  together 
two  volumes  of  nitric  oxide  and  one  volume  of  oxygen, 
both  constituents  being  perfectly  dry.    It  is  an  energetic 
oxidizing  agent  (§   152,   d).     It  may  be  liquefied   and 
solidified.     In  the  presence  of  water  it  forms  acid  com- 
pounds, probably  a  mixture  of  nitric  and  nitrous  acids. 

Experiment  85.—  Pass  250  cu.  cm.  of  0  into  a  bottle  filled  with 
H2O,  colored  with  blue  litmus.     Then  pass  in  250  cu,  cm,  of  NO. 


NITROGEN  OXIDES. 


$88 


Red  fumes  of  NOo  are  produced  but  soon  absorbed  by  the  H20.    Pass 

in  another  250  cu.  cm.  of  NO. 
If  the  0  and  NO  are  pure, 
the  0  will  be  wholly  used  to 
form  N0._  all  of  which  will  be 
absorbed  by  the  H,0.  The 
acids  thus  produced  turn  the 
colored  water  from  blue  to 
red. 

88.  Composition.— 

The    composition    of   ni- 
trogen peroxide,   by  vol- 
ume and  by  weight,  may 
be  represented  as  follows : 


N02 
46  m.  c. 


§9.  Nitrogen  Peiitoxide.  —  Nitrogen  pentoxide  (nitric 
anhydride,  N  205)  is  a  crystalline  white  compound,  so  unstable  that  it 
spontaneously  decomposes  in  a  sealed  tube  into  oxygen  and  nitrogen 
peroxide.  It  is  particularly  interesting  on  account  of  its  relation  to 
nitric  acid. 

NS05  +  H20=2HN03. 

90.  Law  of  Definite  Proportions.— The  truth 
stated  in  §  12  has  been  verified  by  numberless  analyses 
and  may  be  formulated  as  follows  :  Any  given  chemical 
compound  always   contains  the  same  elements  in 
the  same  proportions. 

91.  Law  of  Multiple  Proportions.  —  //  two 

substances  coiribine  to  form  more  than  one  com- 
pound, the  iveight  of  one  substance  being  considered 
as  constant,  the  weights  of  the  other  vary  according 
to  a  simple  ratio. 


NITROGEN  OXIDES. 


73 


(a.)  This  important  principle  is  best  illustrated  by  the  nitrogen 
oxides  just  studied. 


BY  GRAVIMETRIC           BY  VOLUMETRIC 

ANALYSIS. 

ANALYSIS. 

a 

ACTUAL 

RATIO 

ACTUAL 

RATIO 

NAMES. 

1 

z       0 

z    6 

z     0 

z    o 

02 

S             0 

•s  -s 

0        0 

0        O 

S     £ 

•a    -a 

to    "Si 

s    a 

a    a 

01              <U 

1  s 

1  1 

£  £ 

Nitrogen  monoxide 

N20 

28  :  16 

If  :1 

2  :  1 

2  :  1 

Nitric  oxide  

NO 

14  :  16 

If  :2 

1  •  1 

2  :  2 

Nitrogen  trioxide,  . 

N203 

28  :  48 

lf:3 

2  :  3 

2  :  3 

Nitrogen  peroxide. 

N02 

14  :  32 

If:  4 

1  :  2 

2  :  4 

Nitrogen  pentoxide 

N205 

28  :  80 

lf:5 

2  :  5 

2  :  5 

Attention  is  called  to  the  consecutive  numbers,  1,  2,  3,  4,  and  5,  in 
the  columns  headed  "  Ratio." 

(&.)  This  law  necessarily  results  from  the  definition  of  an  atom 
(§  5).  Since  the  atoms  can  not  be  divided,  the  elements  can  combine 
only  atom  by  atom  and,  consequently,  either  in  the  ratio  of  their 
atomic  weights  or  some  simple  multiple  of  that  ratio. 

EXERCISES. 

1.  Is  the  air  a  mixture  or  a  compound  ?    Why  ? 

2.  State  the  points  of  resemblance  and  difference  between  0  and  N. 
8.  (a.)  Is    the    process  of   preparing    O   analytic  or   synthetic? 

(6.)  Of  preparing  N02  ?    (c.)  N30  ?    k 

4.  How  could  you  prove  the  presence  of  0  in  air  ? 

5.  If  two  liters  of  N  and  one  of  0  be  combined,  what  will  be  the 
name  and  volume  of  the  product  ?  <£ 

6.  (a.)  How  is  ammonia  water  prepared  ?    (&.)  How  is  liquid  am- 
monia prepared  ?    (c.)  What  will  result  from  the  decomposition  of  a 
liter  of  laughing  gas  into  its  constituent  elements  ?    (d.)  Write  the 
reaction  for  the  preparation  of  NH3. 

7.  When  N20  is  mixed  with  H  and  the  mixture  exploded,  N  and  a 
compound  vapor  are  formed.    Write  the  reaction. 


^// 


V, 

QUANTIVALENCE,    RATIONAL  SYMBOLS,    RADICALS. 


92.  Quail tivalence. — In  hydrochloric  acid  (HCI), 
one  atom  of  chlorine  unites  with  one  of  hydrogen.  In 
water,  one  atom  of  oxygen  unites  with  two  of  hydrogen. 
In  ammonia,  one  atom  of  nitrogen  unites  with  three  of 
hydrogen.  In  marsh  gas  (CH4),  one  atom  of  carbon 
unites  with  four  of  hydrogen.  One  atom  of  potassium 
may  replace  one  atom  of  hydrogen  in  nitric  acid  (HN03) 
yielding  potassium  nitrate  (KN03),  while  one  atom  of 
copper  replaces  two  atoms  of  hydrogen  in  sulphuric 
acid  (H2S04)  forming  copper  sulphate  (CuS04).  One 
atom  of  potassium  can  replace  one  atom  of  hydrogen, 
but  no  more ;  one  atom  of  copper  can  replace  two  atoms 
of  hydrogen,  but  no  less.  The  quantivalence  of  an 
atom  or  group  of  atoms  (§97)  expresses  the  num- 
ber of  hydrogen  atoms  ivith  which  it  can  combine 
or  for  ivhich  it  may  be  exchanged  ;  e.  g.>  the  quan- 
tivalence of  potassium  is  one,  that  of  oxygen  is  two. 

(a.)  Atoms  are  classified  according  to  their  quantivalence  as  monads, 
dyads,  triads,  tetrads,  pentads,  hexads  and  heptads,  from  the  Greek 
numerals.  They  are  similarly  described  by  the  adjectives  univalent, 
bivalent,  trivalent,  quadrivalent,  quinquivalent,  sexivalent,  and  sep- 
tivalent,  from  the  Latin  numerals.  Thus,  oxygen  is  a  dyad,  or  it  is 
bivalent ;  carbon  is  a  tetrad,  or  it  is  quadrivalent. 

(&.)  The  quantivalence  of  an  element  may  be  absolute  or  apparent. 
Absolute  (or  true)  quantivaleuce  is  conceived  to  be  a  property  of 


§  94  SYMBOLS.  75 

atoms,  invariable  for  any  one  atom  under  like  conditions.  It  is  a 
power  that  may  or  may  not  be  exerted  to  its  full  extent.  With  our 
present  limited  knowledge,  it  is  impossible  to  determine  the  absolute 
quanti valence  of  an  element  with  certainty.  Apparent  quantivalence 
is  the  combining  power  that  an  atom  exhibits  in  any  given  compound. 
It  may  or  may  not  be  the  same  as  its  absolute  quantivalence.  The 
quantivalence  of  N  apparent  in  NH3  is  three  ;  i.  e.,  N  there  appears 
to  be  a  triad.  Its  quantivalence  apparent  in  N  H  4  C I  is  five  ;  it  there 
appears  as  a  pentad.  When  atoms  of  the  same  element  act  with 
different  quantivalences,  they  frequently  form  compounds  as  dis- 
similar as  atoms  of  different  kinds  would  do.  A  change  in  the  appar- 
ent quantivalence  of  an  atom  implies  a  change  in  all  of  its  chemical 
relations.  N20  is  as  different  from  N20-  as  H20  is. 

(c.)  The  quantivalence  of  an  atom  is  indicated  by  Roman  numer- 
als placed  above,  or  minute  marks  placed  above  and  at  the  right 

IV 

of  the  symbol,  as  C  or  N'".  They  should  not  be  confounded  with 
the  figures  below  and  at  the  right  of  the  symbol. 

(d.)  Sometimes  the  words  "valence,"  "equivalence"  and  "atom- 
icity "  are  used  in  the  sense  in  which  we  have  used  the  word  quan- 
tivalence. The  word  "  atomicity"  more  properly  refers  to  the  num- 
ber of  atoms  in  a  molecule. 

(e.)  The  quantivalence  of  many  common  elements  is  not  yet  satis- 
factorily determined.  Quantivalence  should  not  be  confounded  with 
chemism  or  affinity.  H  and  Cl  have  a  very  great  affinity  for  each 
other,  but  each  is  univalent. 

93.  Graphic  Symbols  of  Atoms.— The  graphic 
symbol  of  an  atom  represents  its  quantivalence  by  lines  or 
bonds  radiating  from  the  symbol,  as  follows  : 

Monad,        Dyad,        Triad,        Tetrad,        Pentad,        Hexad. 
H—  0=  N=  C=  =P=          =S= 

The  number  of  bonds  is  significant ;  their  direction  is  not. 
Thus,  the  graphic  symbol  of  an  atom  of  oxygen  may  be 
written  -0-,  0=,  0-,  -0,  Ck,  etc.,  etc. 

94.  Empirical    and    Rational    Symbols.— 

Molecular  symbols  are  of  two  classes,  empirical  and  rational. 
An  empirical  symbol  is  based  upon  analysis,  expresses  the 


76  SYMBOLS.  §  94 

kind  and  number  of  atoms  in  a  molecule,  and  represents 
all  that  we  Tcnoiv  about  the  constitution  of  the  molecule. 
H20,  HN03,  etc.,  are  empirical  symbols.  A  rational  sym- 
bol attempts  to  represent,  in  addition  to  this,  the  possible 
modes  of  formation  and  decomposition  of  substances 
and  are  sometimes  necessary  to  enable  us  to  distinguish 
between  substances  having  the  same  empirical  symbol  but 
endowed  with  different  properties  (§  216).  Graphic  and 
typical  symbols  are  included  under  this  head. 

95.  Graphic    Symbols.  —  A    constitutional    or 
graphic  symbol  is  one  that  indicates  the  constitution  of  a 
molecule;  not,  indeed,  by  showing  the  arrangement  of  the 
atoms  in  space,  for  we  know  nothing  at  all  about  that,  but 
by  showing  which  atoms  are  united  with  each  other  in  the 
molecule.    It  is  composed  of  the  graphic  symbols  of  the 
constituent  atoms : 

(a.)  The  graphic  symbol  of  H00  may  be  written  H-O-H  ;  that  of 
H  0 

H3N,  H-N-H;  that  of  CO2,  0  =  C=0;  that  of  HN08,  H-O-N  =  0 

and  that  of  S00,  0=S=0.     It  will  be  noticed  that  each  atom  has 

II 
the  number  of  bonds  that  represents  its  quantivalence. 

96.  Typical    Symbols.  —  Chemical  symbols  are 
sometimes  written  in  accordance  with  one  of  several  types, 
e.  g.,  free  hydrogen  or  hydrochloric  acid,  water,  ammonia 
and  marsh  gas. 

The  underlying  idea  is  that  the  chemical  constitution  of 
all  known  substances  is  modelled  upon  a  limited  number 
of  types.  By  replacing  atomic  symbols  in  the  type  by 
others  of  the  same  quantivalence,  we  can  obtain  the  sym- 
bol for  any  other  member  of  the  class. 


§97 


RADICALS. 


77 


(a.)  Examples  of  typical  symbols  are  given  below  : 


Free  Hydrogen. 


Water. 


Ammonia. 


HI 

H  IN 

H/ 


Hydrochloric 
Acid. 

Sodium 
Hydrate. 

Methyl- 
amine. 

U     ) 

(CH.)n 

n   ( 

cif 

H"}° 

H     IN 
H    J 

Methyl 
Hydride. 

Sulphuric 
Add. 

Trimethyl- 
amine. 

Methyl 
SUicide. 


CM 

CH 


|N 


(6.)  These  typical  symbols  are  not  to  be  considered  as  suggesting 
similar  properties  in  the  substances  referred  to  any  one  type.  They 
simply  suggest  similarity  in  the  supposed  grouping  of  the  atoms  in 
the  molecule. 

(c.)  It  will  be  noticed,  from  the  examples  above,  that  a  compound 
radical  (§  97)  may  take  its  proper  place  in  a  typical  symbol,  replacing 
an  atom  or  more  of  H  according  to  its  quantivalence  and  that  a  sub- 
stance  (e.  g.,  H2S04)  may  be  represented  as  built  upon  the  type  of 
the  double  molecule  of  the  typical  compound.  A  triple  molecule 


may  be  thus  used,  e.  g.,  glycerin  = 


0. 


(<?.)  Typical  symbols  are  of  great  assistance  in  classification,  es- 
pecially in  the  case  of  the  carbon  compounds. 

97.  Simple  and   Compound  Radicals.  —  An 

atom  or  group  of  atoms  that  seems  to  determine  the  char- 
acter of  a  molecule  is  called  a  radical.  Such  an  atom  is 
called  a  simple  radical  ;  such  a  group  of  atoms  is  called  a 
compound  radical.  In  the  graphic  symbols  given  above, 
it  will  be  noticed  that,  in  each  case  but  one  (S02)>  every 
atom  has  its  quantivalence  fully  satisfied  ;  i.  e.,  each  bond 
of  each  atom  is  engaged.  Such  atomic  groups  are  said  to 


78  RADICALS.  §  97 

be  saturated.  But  the  group,  0  =  S=0,  has  two  free  bonds. 

Such  an  unsaturated  group  of  atoms  is  called  a 
compound  radical.  It  may  enter  into  combination 
like  a  simple  atom,  always  acting  with  a  quan- 
tivalence equal  to  the  number  of  unsatisfied  bonds. 

(a.)  The  names  of  compound  radicals  generally  terminate  in  -yt, 
as  nitrosyl  (NO)  and  nitryl  (N02).  Two  of  these  atomic  groups  may 
unite,  like  two  atoms,  to  form  a  saturated  molecule.  If,  from  H-O-H, 
we  remove  one  atom  of  H,  we  have  the  compound  radical  H-0-, 
called  hydroxyl.  Two  of  these  univalent  groups  may  unite  to  form 
H202  (§  44),  as  follows  :  (HO)-<HO)  or  H-O-O-H. 

EXERCISES,  e^ 

1.  Considering  C I  to  be  a  monad,  write  the  graphic  symbols  for 
CI80,  CI208,  HCiOandHCI03. 

2.  What  quantivalence  for  Cl  is  indicated  by  the  symbol — 

H-O-C  =0?  Jf 

0 

3.  Write  three  graphic  symbols  for  S02,  two  of  which  shall  rep- 
resent it  as  a  compound  radical  (sulphuryl)  and  all  of  which  shall 
represent  S  as  a  dyad. 

4.  Write  two  graphic  symbols  for  S03,  one  of  them,  representing^  ^ 
S  as  a  dyad,  the  other  representing  S  as  a  hexad. 

5.  Name  the  substances,  symbolized  as  follows,  indicating  the  sym- 
bols for  compound  radicals  : 

N  =  N  0  =  N\      /f^ 

V   ;  °J      0  =  N/0'' 

H-O-N'?; 

HtC°     H-°-N  =  ° 

State  the  difference  between  the  indications  given  by  the  last  two 
symbols. 


V, 

THE     HALOGEN     GROUP. 


ffiOECTION  I 

CH  LORINE. 


Symbol,  Cl ;  specific  gravity,  35.5 ;  atomic  weight,  35.5  m.  c. ; 
molecular  weight,  71  m.  c. ;  quantivalence,  1,  (3,  5,  or  7). 

98,  Occurrence.  — Chlorine  does  not  occur  free  in 
nature,  but  it  is  very  abundant  and  widely  diffused,  being 
a  constituent  of   common  salt    (sodium  chloride,  NaCI), 
and  of  potassium  chloride  (KC1).    Every  liter  of  sea-water 
may  be  made  to  yield  about  five  times  its  volume  of 
chlorine. 

Note. — The  name  comes  from  the  Greek  chloros,  meaning  green. 
The  elementary  character  of  chlorine  is  seriously  questioned,  but  the 
gas  has  not  yet  been  shown  to  be  compound, 

99.  Preparation.— Chlorine  is  generally  prepared, 
directly  or  indirectly,  from  common  salt  (NaCI). 

(a.)  Melt  a  small  quantity  of  NaCI  in  a  Hessian  crucible  over  a  coal 
fire,  and  pour  the  fused  salt  upon  a  stone  slab  or  brick  floor.  Wher 
the  NaCI  is  cool,  put  about  30  #.  of  it  into  a  liter  Florence  flask,  add 
30  g.  of  manganese  dioxide  (MnO2)  and  35  cu.  cm.  of  strong  sulphuric 
acid  (H2SO4),  previously  diluted  with  an  equal  bulk  of  H20.  The 
stopper  of  the  flask  should  have  a  delivery  tube  passing  to  the  bottom 
of  a  tall,  dry,  glass  cylinder.  It  is  well  to  provide  a  safety  tube 
(App.  12)  for  the  flask.  Shake  the  flask  to  mix  the  materials,  place  it 
upon  a  sand  bath  and  heat  gently.  Cl  is  evolved  and  is  collected  in  tho 
cylinder  by  downward  displacement.  When  the  cylinder  is  full, 


80 


CHLORINE. 


close  the  mouth  with  a  greased  glass  plate.    The  yellowish  green 

color  of  the  gas  enables  the  ex- 
perimenter to  see  when  the  cylin- 
der is  full.  Be  careful  not  to  in- 
hale the  gas.  Perform  all  experi- 
ments with  Cl  in  a  draught  of  air 
or  in  a  ventilating  closet  (App.  23) 
if  you  have  one. 

2NaCI  +  Mn02  +  3H2S04  = 


MnS04  +  2HNaS04 

+  CI2. 


2H0 


(6.)  Another  way  of  preparing 
Cl    is  to   use  12  g.  of  Mn02  and 
25  cu.  cm.  of  hydrochloric  (mu- 
FIG.  42.  riatic)  acid  instead  of  the  NaCI, 

Mn02  and  H2S04.     The  gas  may  be  collected,  although  with  loss, 
over  hot  water  or  strong  brine. 


4HCI 


Mn03  =  MnCU 


(c.)  The  easiest  way  of  preparing  Cl  is  to  put  a  small  bottle  of 
chloride  of  lime,  bleaching  powder  (CaOC  1  2),  say  15  or  20  g.,  into 
the  bottom  of  a  glass  vessel  of  several  liters  capacity,  and  then,  by 
means  of  a  funnel  tube  passing  through  the  pasteboard  cover  of  the 
large  jar,  to  pour  dilute  H2S04  upon  the  CaOCI2. 

Experiment  86.  —  Prepare  some  chlorine  water  by  passing  a  current 
of  Cl  through  H20,  in  a 
series  of  Woulffe"  bottles, 
arranged  as  in  Exp.  65,  ex- 
cept that  the  tubes  should 
not  dip  so  far  under  the  sur- 
face of  the  HoO.  The  solu- 
tion formed  is  heavier  than 
H20.  The  chlorine  water 
may  be  preserved  for  a  con- 
siderable time  by  placing  it 
in  bottles  wrapped  in  opaque 
paper  and  closed  with 
greased  stoppers.  If  we 
wish  to  absorb  the  whole  of 
a  small  quantity  of  Cl,  we 
may  pass  it  into  an  inverted 
retort  filled  with  H20,  as  shown  in  Fig.  43. 


§  100  CHLORINE.  81 

Experiment  87.— Into  a  jar  filled  with  Cl,  pour  H20  until  the  jar 
is  a  third  full  of  the  liquid.  Close  the 
mouth  of  the  bottle  with  the  hand  and 
shake  the  bottle.  The  gas  will  be  ab- 
sorbed, a  vacuum  formed  and  the  bottle 
held  against  the  hand  by  atmospheric  pres- 
sure (Fig.  44). 

1OO.  Physical  Properties.—  1} 

Chlorine  is  a  yellowish  green,  irres- 
pirable  gas  with  a  suffocating  odor  FlG-  44- 

and  astringent  taste.  Even  a  very  small  quantity  of  it  in 
the  air  produces  violent  coughing  and  irritation  of  the  air 
passages,  when  it  is  inhaled.  Any  attempt  to  breathe  it 
undiluted  would  doubtless  prove  fatal.  It  is  about  2£  times 
as  heavy  as  air,  one  liter  weighing  35.5  criths.  It  may  be 
liquefied  by  pressure  or  cold.  It  is  largely  soluble  in 
water,  one  volume  of  which,  at  10°C.,  dissolves  2£  vol- 
umes of  the  gas.  The  solution  has  most  of  the  proper- 
ties of  the  gas,  and,  when  saturated,  gives  off  the  gas 
freely  on  exposure  to  the  air. 

Experiment  88. — Fill  a  tall  bottle  or  cylinder  holding  500  cu.  cm. 
or  more  with  Cl.  The  gas  may  well  be  dried  by  passing  it  over  cal- 
cium chloride,  as  in  Exp.  28,  or  by  passing  it  over  fragments  of 
pumice  saturated  with  sulphuric  acid  (H2S04),  as  in  Exp.  31,  or  by 
allowing  the  gas  to  bubble  through  H2S04.  Slowly  sift  freshly 
prepared  filings  of  metallic  antimony  into  the  bottle.  The  two 
elements  will  combine  with  the  evolution  of  heat  and  light.  Filings 
of  metallic  arsenic  or  bismuth  give  similar  effects. 

Experiment  89. — Place  a  thin  slice  of  dry  phosphorus  in  a  deflagrat- 
ing spoon  and  place  it  in  a  jar  of  Cl.  The  gas  and  the  solid  com- 
bine directly  with  a  pale  flame. 

Experiment  90.— Burn  a  jet  of  H,  or  illuminating  gas,  in  an  atmos- 
phere of  Cl,  as  represented  in  Fig.  45.  Reverse  the  conditions  and 
burn  a  jet  of  Cl  in  H  (see  Fig.  27).  Try  to  burn  a  jet  of  Cl  in  O, 
and  a  jet  of  0  in  Cl. 


§  100 


FIG.  45. 
Experiment  91. — Pour  chlorine  water  into  a  solution  of  hydrogen 

sulphide  (H2S,  §  137).     The  Cl  robs  the  H2S  of  its  H  to  form  HCI, 

while  the  S  is  precipitated. 

Experiment  9;?.  —  In  a  dark- 
ened room,  mix  equal  volumes 
of  H  and  Cl,  previously  prepared 
in  the  light.  With  the  mixture, 
fill  three  stout  soda  bottles. 
Wrap  one  of  the  bottles  with  a 
towel,  remove  the  cork  anu  up 
ply  a  flame  to  the  mouth  of  the 
bottle.  The  mixed  gases  com- 
bine with  an  explosion.  The 
towel  will  protect  the  experi- 
menter if  the  explosion  break 
the  bottle.  Wrap  the  second 
bottle  with  a  towel  to  which  a 
string,  two  or  three  meters  long, 
has  been  attached.  Carry  the 
covered  bottle  into  a  sunny  place 
FIG.  46.  and,  by  means  of  the  string,  re- 


§100 


CHLORINE. 


83 


move  the  towel.     The  sun's  direct  rays  cause  the  mixed  gases  to  ex- 
plode. 

This  experiment  succeeds  best  with  a  thin  glass  bulb  filled  with 
a  gaseous  mixture  obtained  by  the  electrolysis  of  hydrochloric  acid. 
On  exposing  one  of  these  bulbs  to  bright  day  light,  or  to  the  electric 


FIG.  47. 

or  magnesium  (Fig.  47)  light,  a  sharp  explosion  occurs,  produced  by 

the  synthesis  of  the  gases  prepared  by  electrolytic  analysis. 
Place  the  third  bottle  in  diffused  sun  light.     The  two  gases  will 

unite  gradually  and  quietly.    Allow  the  bottle  to  remain  for  future 

use. 

Experiment  93.— Fill  five  wide  mouthed  bottles  with  dry  Cl  and 
close  their  mouths  with  greased 
glass  plates.  Heat  some  oil  of 
turpentine  (C10H16)  over  the 
water  bath  (App.  10).  Fasten 
a  tuft  of  shredded  tissue  paper 
or  of  cotton  to  a  wire  or  splinter, 
dip  it  into  the  hot  turpentine, 
and  quickly  plunge  it  into  the 
first  bottle  of  Cl.  The  paper  or 
cotton  will  generally  take  fire 
and  burn  with  a  very  dense 
smoke  (Fig.  48).  Into  the  second 
bottle,  thrust  a  burning  dry 
FIG.  48.  wood  splinter;  into  the  third,  FlG-  49 


84  CHLORINE.  §  1 01 

thrust  a  burning  piece  of  paper  ;  into  the  fourth,  a  burning  wax  or 
tallow  taper  (Fig.  49) ;  into  the  fifth,  a  deflagrating  spoon  containing 
burning  petroleum.  Note  the  effect  in  each  case. 

Note. — The  combustibles  used  in  the  last  experiment  contain  H  and 
carbon  (C).  This  H  combines  with  the  Cl  and  sets  the  C  free,  as 
smoke. 

Experiment  94. — Fill  a  tall  tube  with  Cl  and  invert  it  over  a  cup 
of  H20.  Place  the  tube  in  a  sunny  place.  After  a  few  days,  test  the 
gaseous  contents  of  the  tube  for  0,  and  the  water  for  an  acid.  Seek 
for  the  odor  of  Cl. 

Note. — If  two  volumes  of  olefiant  gas  (CgH^)  be  mixed  with  four 
volumes  of  Cl,  the  C  will  be  set  free,  as  dense  smoke  ;  C8H4  +  2CI2 
=:  4HCI  +  C2.  If  the  air  be  exhausted  from  a  flask  containing  a  few 
leaves  of  "Dutch  metal"  (very  thin  copper)  and  Cl  admitted  into 
the  vacuum,  the  copper  leaf  will  burn,  forming  yellow  fumes  of  cop- 
per chloride.  If  sodium  be  melted  in  a  spoon  and  placed  in  a  jar  of 
moist  Cl,  the  synthesis  will  yield  common  salt :  Na  +  Cl  =  NaCI. 
Potassium  is  similarly  attacked  by  either  moist  or  dry  Cl. 

1O1.  Chemical  Properties.  —  Chlorine  is  a  very 
energetic  chemical  agent.  It  unites  directly  with  all  of 
the  elements  except  oxygen,  nitrogen  and  carbon,  its  at- 
traction for  hydrogen  being  very  remarkable.  It  is  even 
able  to  decompose  water,  combining  with  the%  hydrogen 
and  liberating  the  oxygen. 

Experiment  95. — Pass  a  current  of  dry  Cl  through  a  bulb  or  U-tube 
containing  a  bit  of  dry  calico  print.  After  a  few  moments,  attach  a 
second  tube  containing  a  bit  of  similar  calico  that  has  been  moistened. 
Notice  that  the  Cl  now  passes  the  dry  calico  without  bleaching  it, 
but  that  it  quickly  bleaches  the  moist  calico  with  which  it  subse- 
quently comes  into  contact. 

Note. — Pink  or  blue  paper  cambric  is  desirable  for  the  above  ex 
periment. 

Experiment  96.  — Nearly  fill  seven  test  tubes  with  chlorine  water. 
Into  the  first,  pour 'a  few  drops  of  indigo  solution  ;  into  the  second, 
litmus  solution  ;  into  the  third,  cochineal  solution  ;  into  the  fourth 
and  fifth,  aniline  dyes  of  different  colors;  into  the  sixth, the  colored 
petal  of  a  flower,  and  into  the  seventh  put  a  strip  of  colored  calico  or 
paper  cambric.  The  colors  will  quickly  disappear. 


§  102  CHLORINE.  85 

Experiment  97. — Upon  a  piece  of  printed  paper,  write  your  name 
in  ink,  Dip  the  paper  into  chlorine  water.  The  written  characters 
will  be  bleached  out ;  the  printed  characters  will  remain. 

Experiment  98. — Repeat  Exp.  91,  noticing  the  odor  of  H3S  before 
the  addition  of  the  chlorine  water  and  its  absence  after  such  addition. 

1O2.  Uses. — Chlorine  is  of  great  use  in  the  arts  as  a 
bleaching  and  disinfecting  agent,  its  action  depending  very 
largely  upon  its  attraction  for  hydrogen.  The  non-mineral 
coloring  matters  are  largely  composed  of  oxygpn,  hydrogen, 
nitrogen  and  carbon.  When  such  coloring  irfatter  is 
brought  into  contact  with  chlorine  in  the  presence  of 
moisture,  the  chlorine  attacks  the  hydrogen  of  both, 
the  nascent  oxygen  thus  liberated  from  the  water  greatly 
aiding  the  chlorine  in  the  decomposition  of  the  coloring 
substance.  Colorless  compounds  are  formed  by  a  process 
of  chlorination  and  oxidation.  Chlorine  has  little  effect 
upon  mineral  or  carbon  colors. 

Experiment  99. — Prepare  a  quantity  of  thin  starch  paste  by  boiling 
80  cu.  cm.  of  H2O  and  stirring  into  it  0.5  g.  of  starch  previously  re- 
duced to  the  consistency  of  cream  by  thoroughly  mixing  with  a  few 
drops  of  H80.  In  this  paste,  dissolve  a  piece  of  potassium  iodide, 
half  the  size  of  a  pea.  Into  a  test  tube,  put  10  cu.  cm.  of  H20  and 
5  or  6  drops  of  this  mixture  of  starch  and  potassium  iodide.  Shake 
the  tube  vigorously  for  a  few  seconds  and  let  a  few  drops  of  chlorine 
water  fall  into  it.  Notice  the  blue  color  thus  formed. 

Experiment  100. — Into  the  solution  of  starch  and  potassium  iodide, 
dip  two  or  three  strips  of  white  paper.  Hold  one  of  these  strips  of  test 
paper  in  a  current  of  Cl.  The  white  paper  is  turned  to  blue.  Re- 
move the  stopper  from  the  bottle  containing  chloride  of  lime  (bleach- 
ing powder)  and  hold  another  strip  of  the  test  paper  in  the  atmosphere 
of  Cl  that  fills  the  upper  part  of  the  bottle.  The  paper  is  instantly 
colored  blue. 

Note. — The  Cl  decomposes  the  potassium  iodide ;  the  free  iodine 
colors  the  starch  (see  Exp.  121). 

Experiment  101. — Place  a  strip  of  gold  leaf  in  saturated  chlorine 
writer.  The  gold  will  be  dissolved. 


86  CHLORINE.  §  103 

Experiment  102.  —  Dissolve  a  few  crystals  of  silver  nitrate 
(AgN03)  in  H20.  Add  a  few  drops  of. a  solution  of  common  salt 
(NaCI).  A  white  curdy  precipitate  of  silver  chloride  (AgCI)  is 
formed. 

Experiment  103. — Wash  the  AgCI  obtained  in  the  last  experiment 
and  try  to  dissolve  it  in  HN03.  It  will  prove  to  be  insoluble  in 
that  liquid. 

Experiment  104. — Wash  the  AgCI  of  the  last  experiment  and  try  to 
dissolve  it  in  strong  ammonia  water.  It  will  dissolve. 

103.  Tests.  —  Free  chlorine  is  easily  distinguished 
by  its  odor;  pnre  chlorine,  by  its  color.  Chlorine  is  also 
easily  detected  by  its  bleaching  action  upon  organic  color- 
ing matters,  or  by  its  forming  a  blue  color  with  a  mixture 
of  starch  and  potassium  iodide.  This  last  mentioned  re- 
action is  very  delicate,  but  an  excess  of  chlorine  removes 
the  color  and  the  same  effect  is  produced  by  bromine,  ozone 
and  a  few  other  actively  oxidizing  substances.  Many  of 
its  compounds  yield,  with  solutions  of  silver  salts,  precip- 
itates of  silver  chloride,  insoluble  in  nitric  acid. 

(a.)  By  adding  a  solution  of  silver  nitrate  to  that  of  a  soluble 
chloride  (e.  g.,  KCI  +  AgN03),  one  part  of  Cl  in  a  million  parts  of 
H20  may  be  detected,  a  faint  opalescence  appearing. 

•     r6 

£,)  EXERCISES. 

1.  When  chlorine  water  is  exposed  to  sunlight,  HCI  is  formed  and 
0  is  set  free,     (a.)  Write  the  reaction.     (6.)  What  volume  of  Cl  is 
necessary  thus  to  set  free  20  cu.  cm.  of  0  ? 

2.  Cl  unites  with  the  metals  acting  as  a  monad.     («.)  Symbolize  the 
binary  compounds  of  Cl   with  the  following:   Na';  K' ;  Cu" -,  Au'"  ; 
Ag' ;  Fe"  ;  Zn"  ;  (Fe2)T'.      (&.)  Symbolize  the  nitrates  formed  by  re- 
placing the  H  in  HN08  by  the  several  metals  just  mentioned. 


105 


HYDROCHLORIC   ACID. 


87 


HYDROCHLORIC    ACID. 

104.  Source.— Hydrochloric  acid  (hydrogen  chloride, 
chlorhydric  acid,  muriatic  acid,  HCI)  is  the  only  known 
compound  of  hydrogen  and  chlorine.     The  hydrogen  is 
generally  furnished  by  sulphuric  acid  (H2S04)  and  the 
chlorine   by  common   salt   (sodium   chloride,   NaCI),  the 
cheapest  and  most  abundant  source  of  chlorine.    The  pure 
acid  is  a  gas,  the  aqueous  solution  of  which  constitutes 
the  muriatic  acid  of  commerce. 

(a.)  HCI  is  found  in  the  exhalations  of  active  volcanoes,  especially 
Vesuvius  and  Hecla,  and  in  the  waters  of  several  South  American 
rivers  that  have  their  rise  in  volcanic  regions. 

105.  Preparation.  —  Hydrochloric  acid  is  almost 
always  prepared  from  common  salt  by  distillation  with  sul- 

• 

phuric  acid. 

(a.)  Into  a  liter  Florence  flask, 
put  30  g.  of  fused  NaCI  and  30 
cu.  cm.  of  H2  SO  4.  Heat  the 
flask  gently  over  the  sand  bath 
and  collect  by  downward  dis- 
placement in  dry  jars,  as  in  the 
preparation  of  Cl.  By  holding  a 
piece  of  moistened  blue  litmus 
paper  at  the  mouth  of  the  jar, 
the  experimenter  may  easily  tell 
when  the  jar  is  full.  Compare 
this  paragraph  carefully  with 
£74. 

NaCI  +  H3S04  =  HCI+  HNaS04. 
(&.)  At  a  higher  temperature, 


FIG.  50. 


HYDROCHLORIC    ACID. 


§105 


the  same  quantity  of  H3S04  would  combine  with  twice  as  much 
NaCI,  yield  twice  as  much  HCI,  and  leave  sodium  sulphate  (Na2S04) 
instead  of  hydrogen  sodium  sulphate  (HNaS04),  according  to  this 
equation  : 

2NaCI  +  H2S04  =  2HCI  +  Na2S04. 

The  greater  heat  necessary  for  this  latter  reaction  would  be  severe 
upon  the  apparatus.  At  the  end  of  the  experiment,  the  HNaS04 
remaining  in  the  flask  may  be  easily  removed  with  warm  H20. 

(c.)  HCI  may  be  prepared  by  the  direct  union  of  equal  volumes  of 
its  constituents  (see  FJxp.  92). 

(d.)  In  the  arts,  the  retort  used  is  an  iron  cylinder  and  the  gaseous 
acid  is  dissolved  in  H20,  contained  in  a  series  of  earthenware  Woulffe 
bottles.  In  this  apparatus,  either  of  the  reactions  above  mentioned 
may  take  place.  Very  large  quantities  (thousands  of  tons  weekly) 
of  the  acid  liquid  are  made  as  an  incidental  product  of  the  manufac- 
ture of  sodium  carbonate  (§  268). 

(e.)  Dry,  gaseous 
HCI  may  be  ob- 
tained by  heating 
the  acid  liquid  and 
passing  the  gas 
given  off  through  a 
drying  tube  or  bot- 
tle. Sec  Exp.  61. 

Experiment  105. — 
Fill  a  long  test  tube 
with  dry  HCI  and 
invert  it  over  mer- 
cury. Thrust  a  bit 
of  ice  into  the 
FIG.  51.  mouth  of  the  tube.  FIG.  52. 

The  ice  and  gas  will  quickly  disappear,  the  mercury  rising  in  the 
tube.  Explain. 

Experiment  106. ~ Fill  a  bottle  with  dry  HCI.  Close  the  bottle 
with  a  cork  carrying  a  glass  tube  and  invert  it  over  H20,  colored 
with  blue  litmus  (Fig.  52).  The  H20  will  soon  enter  with  violence, 
and  its  color  will  be  changed  from  blue  to  red.  Instead  of  passing 
the  tube  from  a  into  colored  water  in  an  open  vessel,  as  shown  in  the 
figure,  it  may  be  passed  through  the  cork  of  a  closed  bottle  into  the 


io6 


HYDROCHLORIC    ACID. 


89 


liquid.  If  this  bottle  be  provided  with  a  bent  tube,  air  may  be  forced 
into  the  bottle  and  thus  enough  H20  forced  into  a  to  begin  the  ab- 
sorption without  waiting  for  the  HCI  to  diffuse  downward  through 
the  tube.  Compare  Exp.  64. 


FIG.  53- 

Experiment  107. — Pass  HCI  from  the  generating  flask  through  a 
series  of  Woulffe  bottles  arranged  as  in  Exp.  65,  except  that  the  de- 
livery tube  from  each  bottle  should  barely  dip  into  the  H20  of  the 
next  bottle.  It  is  well  to  place  the  Woulffe  bottles  in  H20  to  keep 
them  cool.  When  the  gas  ceases  to  flow,  test  the  contents  of  each 
bottle  with  blue  litmus  paper.  Bottle  the  liquid  and  save  for  future 


1O6.  Physical  Properties.— Hydrochloric  aoid  is 
a  colorless  gas  having  an  acid  taste  and  pungent  odor.  It 
is  irrespirable  and  neither  combustible  nor  a  supporter  of 
combustion.  It  is  a  little  heavier  than  air,  its  specific 
gravity  being  18.25,  i.  e.,  a  liter  of  it  weighs  18£  criths 
(1.6352  g.).  It  liquefies  under  a  pressure  of  40  atmos- 
pheres, this  liquid  having  a  specific  gravity  of  1.27.  The 
gas  is  remarkably  soluble  in  water,  one  volume  of  which, 
at  the  ordinary  temperature,  absorbs  about  450  volumes 
of  the  gas,  or  more  than  500  volumes  at  0°C.  This 
saturated  solution,  the  muriatic  acid  of  commerce,  fumes 
strongly  in  the  air,  has  a  specific  gravity  of  1.21  and 


90  HYDROCHLORIC    ACID.  §  J06 

readily  gives  up  the  acid  gas  when  heated.  If  pure,  it 
freezes  at  temperatures  below  — 40°C.  to  a  butter-like  mass 
having  the  composition  HCI  -f  2H20. 

Experiment  108. — Nearly  fill  a  test  tube  with  dilute,  commercial 
HCI  and  drop  into  it  a  few  pieces  of  granulated  zinc  (see  §  21).  The 
zinc  is  quickly  dissolved.  What  gas  escapes  ?  Write  the  reaction. 

1O7.  Chemical  Properties. —  Hydrochloric  acid 
acts  upon  many  metals  and  their  oxides,  forming  chlorides, 
most  of  which  are  soluble  in  water. 

(a.)  The  liquefied  HCI  does  not  act  upon  any  of  the  metals  ex- 
cept Al. 

Experiment  109. — If  the  second  bottle  used  in  Exp.  92  was  strong 
enough  to  stand  the  explosion  without  breaking,  open  it  with  its 
mouth  under  mercury.  Notice  that  no  mercury  enters  the  bottle 
and  that  no  gas  escapes.  Try  it  with  the  third  bottle  used  in  that 
experiment.  Then  test  the  contents  of  the  bottles  with  moistened 
blue  litmus  paper.  The  reddening  of  the  paper  shows  that  we  have 
an  acid  ;  it  is  HCI.  We  have  shown  that  the  volume  of  the  HCI  is 
the  same  as  that  of  the  gases  that  united  to  form  it.  How  was 
this  shown  f 

Experiment  110. — Fit  a  U  or  V  shaped  tube  to  a  wooden  stand  by 

clamping  it  with  strips  of 
tin  or  cementing  it  with 
plaster  of  Paris.  Through 
each  of  two  corks  pass  a 
wire  attached  to  a  strip  of 
platinum.  Half  fill  the 
tube  with  HCI,  insert  the 
corks  snugly,  push  the 
wires  down  until  the  plati- 
num strips  are  immersed  in 
the  acid  liquid  and  connect 
the  wires  with  the  poles  of  a 
galvanic  battery(Ph.,§§  397, 

398,  401).  At  the  end  of  four  or  five  minutes,  remove  the  cork  that 
carries  the  negative  electrode  (Ph.,  §  377)  and  apply  a  lighted  match. 
H  was  present,  mixed  with  the  air  that  was  in  that  arm  of  the  tube  at 
the  beginning  of  the  experiment.  Remove  the  other  cork  and  thrust 
a  bit  of  moistened  litmus  or  turmeric  paper  into  that  arm  of  the 


§110  HYDROCHLORIC   ACID.  91 

tube.  The  bleaching  of  the  paper  and  the  peculiar  odor  show  the 
presence  of  Cl.  Of  course,  delivery  tubes  may  be  provided  for  the 
corks  and  the  gases  collected  separately  (see  Fig.  4).  Exact  experi- 
ments of  this  kind  are  difficult  on  account  of  the  solubility  of  Cl  in 
H20,  but  when  made  they  show  that  equal  volumes  of  H  and  of  Cl 
are  liberated. 

1O8.  Composition.  —  The  composition  of  hydro- 
chloric acid  has  been  accurately  determined,  both  analyti- 
cally and  synthetically.  Such  determinations  show  that 
one  volume  of  hydrogen  combines  with  one  volume  of 
chlorine  to  form  two  volumes  of  hydrochloric  acid  gas. 
The  composition  maybe  graphically  represented  as  follows: 


The  chemical  action  effects  neither  volumetric  nor  gravi- 
metric change.  It  should  be  noticed  that  hydrochloric 
acid  differs  from  most  of  the  other  acids  in  that  it  contains 
no  oxygen  (§  60). 

109.  Uses. — Hydrochloric  acid  is  used  in  preparing 
chlorine,  potassium  chlorate    (§   281),  chloride   of  lime 
(bleaching  powder,  §  292),   ammonium  chloride,  etc.,  etc. 
It  is  of  very  frequent  use  in  the  chemical  laboratory  and 
has  become  almost  indispensable  in  the    manufacturing 
arts.     It  acts  directly  upon  most  of  the  metals,  forming 
metallic  chlorides,  e.  g.,  zinc  chloride. 

Experiment  111.— Repeat  Exps.  6, 102,  103  and  104,  using  a  solu- 
.tton  of  HCI  instead  of  the  solution  of  NaCI,  mentioned  in  Exp.  102. 

110.  Tests. — Hydrochloric  acid  gas  may  be  detected 
by  its  reddening  moistened  blue  litmus  paper  and  its  form- 
ing dense  fumes  of  ammonium  chloride  (NH4CI)   when 
brought  into  contact  with  ammonia  gas  (Exp.  6).      Its 


92  HYDROCHLORIC    ACID.  §110 

aqueous  solution  may  be  detected  by  its  reddening  blue 
litmus  paper  and  forming,  with  a  solution  of  silver  nitrate, 
a  precipitate  (AgCI)  soluble  in  ammonia  water  but  insolu- 
ble in  nitric  acid. 

EXERCISES. 

1.  When  ammonium  chloride  (sal  ammoniac,  NH4CI)  is  acted  upon 
by  H2S04,  we  have  a  reaction  partly  represented  as  follows  : 

2NH4CI  +  H2S04=(NH4)2S04  + 
Complete  the  equation. 

2.  A  strip  of  paper  moistened  with  a  certain  solution  and  exposed 
to  Cl  turns  blue,     (a.)  What  is  the  solution  ?    (&.)  Explain  the  reac- 
tion,   (c.)  What  other  gas  will  produce  the  same  change  of  color? 

3.  The  vapor  of  mercury  is  100  times  as  heavy  as  H.     The  atomic 
weight  of  mercury  is  200  m.  c.     What  is  the  number  of  atoms  in  a 
mercury  molecule  ?      / 

4.  Show  that  a  molecule  of  H  contains  two  atoms. 

5.  Define  and  illustrate  quantivalence. 

6.  What  is  a  chemical  experiment  ? 


§  III  CHLORINE.   OXIDES.  93 


OTHER    CHLORINE     COMPOUNDS. 

111.  Chlorine  Oxides.  —  Chlorine  does  not  unite 
directly  with  oxygen,  but  it  may  be  made  to  do  so  by  indi- 
rect means.  Five  oxides  of  chlorine  are  recognized  by 
chemists,  of  which  only  three  have  been  isolated. 

(a.)  1.  Chlorine  monoxide  (hypochlorous  oxide)  .......  CI20. 

2.  Chlorine  trioxide  (chlorous  oxide)  .............  CI8O8. 

3.  Chlorine  tetroxide  (chloryl)  ..................  CI204. 

4.  Chlorine  pentoxide  (chloric  oxide)  ............  CI8O5. 

5.  Chlorine  heptoxide  (perchloric  oxide)  .........  CI207. 

(b.)  Cl  20  is  an  explosive,  yellow  gas,  formed  by  passing  dry  Cl  over 
mercuric  oxide  : 

2CI2  +  2HgO  =  Hg8OCI2  +  CI20. 

It  liquefies  at  —  20°C. 

CI203  is  a  greenish,  yellow,  unstable  gas,  prepared  by  the  reduc- 
tion of  chloric  acid,  thus  : 

2HCIC-3  +  N203  =  CI203  +  2HN03. 

CI204  is  an  explosive  gas  obtained  by  the  action  of  sulphuric  acid 
(H2S04)upon  potassium  chlorate  (KC  10  3).  It  is  sometimes  called 
free  chloryl,  the  molecule  being  considered  as  composed  of  two  com- 
pound radicals  : 

0 


0  =  Cl  =  0  or  (ClOa),  thus:         \  -  C\      or 

0  O 

(CI02)-(CI02).  See  §§94,  95.  CI205  and  CI207  have  not  yet  been 
isolated,  but  their  compounds  are  known. 

•  (c.)  Note  the  varying  quantivalence  of  the  Cl  in  these  several 
oxides,  and  that  it  is  represented  by  the  series  of  odd  numbers, 
1,  3,  5  and  7. 

Experiment  112.  —  Pulverize  separately  1  g,  of  sugar  and  1  g.  of 
potassium  chlorate  (KCI03).     Mix  them  intimately  upon  a  piece  of 


NITROGEN    CHLORIDE. 


§112 


paper  and,  from  a  glass  rod  dipped  in  H2S04,  let  a  drop  of  acid  fall 
upon  the  mixture.  The  CI204  thus  set  free  causes  an  energetic  com- 
bastion. 

Experiment  113. -In  a  test  glass,  place  1  g.  of  KCI03  (not  pulver- 
ized). Add  a  few  small  pieces  of  phosphorus 
and  nearly  fill  the  glass  with  H20.  By 
means  of  a  pipette  (App.  5),  bring  H2S04 
into  contact  with  the  KCI03.  The  phos- 
phorus burns  under  H20  in  the  CI204  thus 
set  free. 


Chlorine  Acids.— From 
four  of  these  chlorine  oxides  results  a 
corresponding  list  of  acids  and  salts 
55.  (see  §60).    The  molecular  symbols  for 

the  acids  may  be  obtained  from  those  of  the  correspond- 
ing oxides. 

(a.)  The  addition  of  H20  to  the  symbol  of  the  oxide  will  give  double 
the  symbol  of  the  acid  : 

CI20    +  H20  =  H2CI3O2  =  2HCIO,    hypochlorous  acid. 
CI203  +  H20  =  H2CI204  =  SHClOo,  chlorous  acid. 
Clo05  +  H20  =  H2CI206  =  8HCIO,,  chloric  acid. 
CI207  +  H20  =  HSCI208  =  2HCI04,  perchloric  acid. 

(&.)  The  most  important  of  these  acids  are  HCIO,  because  of  its  re- 
lation to  calcium  hypocklorite,  and  HCI03,  because  of  its  relation  to 
potassium  chlorate. 

(c.)  The  last  two  paragraphs  may  be  summarized  as  follows  : 

sodium  hypochlorite. 
sodium  chlorite. 

potassium  chlorate, 
potassium  perchlorate. 

113.  Nitrogen  Chloride.  —  "  Chlorine  combines 
with  nitrogen,  though  only  indirectly,  to  form  a  very  re- 
markable compound,  the  composition  of  which  has  not 
yet  been  determined.  If  an  excess  of  chlorine  gas  be 


Oxides. 

Acids. 

Salts. 

1.  CI20 

HCIO 

NaCIO, 

2.  CI203 

HCI02 

NaClOo, 

3.  CI204 

? 

? 

4.      ? 

HCI03 

KCI03, 

5.      ? 

HCI04 

KCI04, 

114  §  AQUA    REGTA.  95 

passed  into  a  solution  of  ammonia,  drops  of  an  oily  liquid 
are  seen  to  form,  which,  on  being  touched,  explode  with 
fearful  violence,  so  that  the  greatest  caution  must  be  used 
in  manipulating  even  traces  of  this  body.  The  explosive 
nature  of  this  compound  arises  from  the  fact  that  its  con- 
stituent elements  are  very  loosely  combined  and  separate 
with  sudden  violence." — Roscoe. 

Caution.— Do  not  try  to  prepare  nitrogen  chloride.  It  is  far  too 
dangerous  for  a  school  experiment. 

Experiment  114. — Put  a  small  piece  (4  or  5  sq.  cmf)  of  gold  leaf  into 
a  test  tube  and  pour  in  strong  HN03  until  the  tube  is  a  third  full. 
Put  a  similar  piece  of  gold  leaf  into  another  test  tube  and  pour  in  a 
like  quantity  of  HCI.  If  the  leaf  is  gold  leaf,  neither  liquid  will  dis- 
solve it.  Pour  the  contents  of  one  tube  into  the  other.  The  gold 
leaf  will  quickly  dissolve  in  the  mixed  acids. 

114.  Aqua  Regia. — Gold,  platinum  and  many  metal- 
he  compounds,  are  insoluble  in  either  nitric  or  hydro- 
chloric acid,  but  are  easily  soluble  in  a  mixture  of  these 
acids,  especially  when  heated  in  the  mixture.  The  acids 
react  upon  each  other,  chlorine  is  set  free  and,  in  the 
"  nascent "  condition,  acts  upon  the  metal  or  metallic  com- 
pound more  energetically  than  it  would  otherwise  do. 

.(#.)  The  name  "  aqua  regia  "  (royal  water)  was  given  by  the  old 
alchemists  because  the  mixture  was  able  to  dissolve  gold,  the  "king 
of  metals."  The  mixture  is  sometimes  called  nitro -hydrochloric  acid. 

(&.)  The  expression  "  nascent "  state  or  condition  has  appeared 
before.  It  is  used  to  describe  the  condition  of  a  chemical  agent  at 
the  moment  it  is  set  free  from  some  compound.  What  constitutes 
the  essential  features  of  the  "nascent"  state  is  not  known.  We 
can  not  yet  tell  what  the  difference  between  "  nascent"  H  or  Cl  and 
ordinary  H  or  Cl  is,  but  we  can  tell  what  the  difference  in  their  effects 
is.  The  most  marked  effect  is  greatly  increased  chemical  energy. 
We  shall  see  other  cases  in  illustration  as  we  proceed. 

(c.)  It  is  probable  that  "nascent "  Cl  is  in  the  atomic  condition  and 
ordinary  Cl  in  the  molecular  condition.  They  might  be  symbolized 
as  follows  :  Cl  and  C!8  or  Cl-  and  CI-CI  (§§  93,  94), 


96  AQUA  REGIA.  §  114 

EXERCISES. 

1.  What  chlorine  oxide  has  trivalent  Cl  ? 

2.  (a,)  Write  the  graphic  symbol  for  chloric  acid.      (b.)  What  is 
;    the  quanti valence  of  the  Cl  ? 

3.  («.)  Write  the  graphic  symbol  for  HCI04.    (b.)  "What  is  the 
quanti  valence  of  the  Cl  ? 

4.  Define  atom  ;  atomic  weight ;  microcrith. 

5.  (a.)  If  20  I.  of  H  be  exploded  with  0,  how  many  liters  of  0  will 
be  required?    (&.)  How  many  liters  of  dry  steam  will  be  produced? 

6.  («.)  If  15  1.  of  H  be  mixed  with  10  I  of  0  and  the  mixture  ex- 
ploded, how  many  liters  of  dry  steam  will  be  produced?    (b.)  Will 
any  elementary  gas  remain  free  ?    If  so,  give  its  name  and  volume. 

7.  («.)  How  many  grams  of  H  are  there  in  36  g.  of  H20  ?    (b.)  How 
many  grams  of  0  ?    (c.)  How  many  liters  of  H  ?     (d.)  How  many 

*   liters  of  0  ? 

8.  (a.)  24  I  of  oxygen  will  yield  how  many  liters  of  ozone?    (b.) 
30  I.  of  ozone  is  equal  to  how  many  liters  of  oxygen  ? 

9.  Why  should  Cl—    or    H—    have  greater  affinity  for  another 
element  than  C I— C I  or  H  —  H  ? 

10.  (a.)  How  many  kinds  of  atoms  are  known?    (ft.)  How  many 
kinds  of  molecules  ? 


§  Il6  BROMINE.  97 


BROMINE,     IODINE,   AND     FLUORINE. 


ROMINE  ;   symbol,  Br  ;  specific  gravity,  at  0°C.,  3,187  ;  atomic 
weighty  80  m.  c.  ;  molecular  weight,  160  m.  c.  ;  quantivalence,  1(5  or  7). 

115.  Source.  —  Bromine  does  not  occur  free  in  nature, 
but  is  found  combined  with  metals,  especially  as  magne- 
sium bromide,  in  sea  water  and  in  the  water  of  certain  salt 
wells  and  springs. 

(a.)  Much  of  the  Br  made  in  the  United  States  comes  from  the  salt' 
wells  of  Ohio  and  West  Virginia.  The  bittern  that  remains  after 
the  crystallization  of  the  NaCI  contains  magnesium  bromide  in  such 
quantities  that  Br  is  profitably  extracted  from  it. 

Note.  —  The  name  is  derived  from  the  Greek  Iromos,  meaning  a 
stench. 

Experiment  115.  —  Into  a  flask  of  two  or  three  liters  capacity,  put  a 
few  drops  of  Br  and  cover  the  flask  loosely.  In  a  few  minutes  the 
jar  will  be  filled  with  the  heavy  red  vapor  of  Br, 

Experiment  116.  —  Into  the  jar  of  vaporized  Br,  introduce  a  strip  of 
moistened  litmus  or  turmeric  paper.  It  will  be  bleached. 

Experiment  117.  —  Add  a  few  more  drops  of  Br,  and  after  it  has 
vaporized,  introduce  a  thin  slice  of  dry  phosphorus.  It  will  ignite. 

Experiment  US.  —  Into  a  tall  jar  filled  with  Br  vapor,  let  fall  a  few 
freshly  prepared  filings  of  metallic  antimony.  The  result  is  much 
like  that  of  Exp.  88. 

116.  Properties,    etc.  —  Bromine  is  a  dark  red 
liquid  of  disagreeable  odor,  very  volatile'at  ordinary  tem- 
peratures and  highly  poisonous.     It  is  sparingly  soluble  in 
water  and  easily  soluble  in  ether  or  carbon  disulphide. 
Its  vapor  has  a  -specific  gravity  of  80,  being  more  than  five 

5 


98  IODINE.  §  Il6 

times  as  heavy  as  air.  Its  chemical  properties  closely  re- 
semble those  of  chlorine,  but  it  is  less  active.  Its  attraction 
for  hydrogen  fits  it  for  bleaching  and  disinfecting  uses. 
Some  of  the  bromides  are  used  in  medicine  and  pho- 
tography. 

(a.)  With  the  exception  of  mercury,  Br  is  the  only  element  liquid 
at  ordinary  temperatures. 

(&.)  Br  forms  acids  as  follows:  hydrobromic,  HBr;  hypobromous, 
HBrO  ;  bromic,  HBr03  ;  perbromic.  HBr04.  They  closely  resemble 
the  corresponding  Cl  compounds. 

(c.)  Br,  when  swallowed,  acts  as  an  irritant  poison  ;  when  dropped 
upon  the  skin,  it  produces  a  sore  that  is  very  difficult  to  heal. 

(d.)  Br  has  very  little  action  upon  sodium,  but  combines  energeti- 
cally with  potassium,  sometimes  with  almost  explosive  violence. 

%%T  IODINE;  symbol,  I;  specific  gravity,  4.95 ;  atomic  weight, 
127  m.  c. ;  molecular  weight,  254  »*•  c-  '>  quantivalence,  1(3,5,  or  7), 

117.  Source. — Iodine  compounds  exist  in  very  mi- 
nute quantities  in  the  water  of  the  sea  and  of  some  saline 
springs.  From  sea  water,  the  iodide  is  absorbed  by  certain 
marine  plants.  The  ashes  (kelp)  of  these  sea  weeds  con- 
tain sodium  and  magnesium  iodides.  Iodine  is  obtained 
by  heating  the  kelp  with  sulphuric  acid  and  manganese 
dioxide.  Iodine  is  thus  set  free  in  the  form  of  a  beautiful 
violet  colored  vapor  which  soon  condenses  to  a  solid. 

Experiment  119. — Put  a  small  piece  of  I  into  a  dry  test  tube.  Heat 
the  test  tube  in  the  flame  and  notice  that  the  I  vaporizes  without 
visible  liquefaction  (Ph.,  §  509).  Notice  that  the  vapor  is  very  heavy 
as  well  as  very  beautiful.  If  the  upper  part  of  the  tube  be  cold, 
minute  I  crystals  will  condense  there. 

Experiment  120.—  Place  some  I  upon  a  heated  brick  and  cover  the 
whole  with  a  large  bell-glass.  This  gives  a  good  exhibition  of  the 
beautiful  vapor. 


§  Il8  IODINE.  99 

Experiment  121.— Prepare  some  starch  paste,  as  in  Exp.  99,  and 
dilute  5  or  6  drops  of  it  with  10  cu.  cm.  of  H30.  Dissolve  a  very 
small  piece  of  I  in  alcohol  and  add  a  drop  of  the  alcoholic  solution 
to  the  dilute  starch.  The  starch  will  be  colored  blue  even  when  the 
alcoholic  solution  is  very  dilute.  The  blue  color  will  disappear  upon 
heating  the  solution  and  reappear  upon  cooling  it. 

Experiment  122. — Drop  a  few  crystals  of  I  into  a  large  bottle.  Dip 
a  strip  of  white  paper  into  the  colorless  starch  paste  and  suspend  it 
in  the  bottle.  The  paper  may  be  held  in  place  by  the  stopper  of  the 
bottle.  As  the  I  sublimes  and  diffuses  through  the  bottle,  it  soon 
comes  into  contact  with  the  starch  and  colors  the  paper  blue. 

Note. — A  moment's  reflection  will  show  that  in  this  experiment  the 
quantity  of  I  that  actually  comes  into  contact  with  the  starch  and 
changes  its  color  is  almost  immeasurably  small.  Starch  will  detect 
the  presence  of  one  part  of  I  in  300,000  parts  of  H30. 

Experiment  123. — Add  a  few  drops  of  the  alcoholic  solution  pre- 
pared in  Exp.  121  to  10  cu.  cm.  of  H20  in  a  test  tube.  Owing  to  the 
sparing  solubility  of  I  in  H20,  most  of  the  I  will  be  precipitated. 
Pour  5  cu.  cm.  of  this  aqueous  solution  into  a  test  tube,  add  8  or  10 
drops  of  carbon  disulphide  (CS2)  and  shake  the  contents  of  the  tube. 
On  standing  for  a  few  moments,  the  CS2  will  settle  to  the  bottom, 
when  it  will  be  seen  to  be  colored  purple-red ;  the  color  is  due  to 
the  I  dissolved  in  the  CS2.  Carbon  disulphide  will  detect  the  pres- 
encs  of  one  part  of  I  in  1,000,000  of  H20. 

Experiment  124. — Pour  10  cu.  cm.  of  H20  into  each  of  three  tall 
test  glasses.  Add  a  few  drops  of  a  solution  of  potassium  iodide  to 
each.  To  the  first,  add  a  few  drops  of  a  solution  of  lead  acetate 
(sugar  of  lead).  Brilliant  yellow  lead  iodide  is  formed.  To  the  second, 
add  a  few  drops  of  a  solution  of  mercurous  nitrate.  Yellowish-green 
mercurous  iodide  is  formed.  To  the  third,  add  a  few  drops  of  a  solu- 
tion of  mercuric  chloride  (corrosive  sublimate).  Scarlet  mercuric 
iodide  is  formed. 

118.  Properties,  etc.— Iodine  is  a  blue-black,  crys- 
talline solid  having  a  metallic  lustre.  Its  vapor  has  a 
specific  gravity  of  127  ;  it  is  the  heaviest  known  vapor. 
Iodine  is  very  sparingly  (1:5500  at  10°C.,)  soluble  in  water 
but  readily  dissolves  in  alcohol,  ether,  chloroform,  carbon 
disulphide  or  aqueous  solutions  of  the  metallic  iodides. 


100  LUORINE.  §  H8 

Its  chemical  activity  is  less  than  that  of  bromine.  It  is 
used  in  medicine,  photography  and  the  manufacture  of 
aniline  green.  The  blue  color  it  forms  with  starch,  its 
beautifully  colored  vapor,  and  the  purple-red  color  it  forms 
with  carbon  disulphide  form  delicate  tests  for  free  iodine. 

(a.)  I  forms  acids  as  follows,  hydroiodic,  HI;  iodic  acid,  HI03  ; 
periodic  acid,  H  5IO  6 .  They  closely  resemble  the  corresponding  C I  and 
Br  compounds. 

(&.)  I  has  no  action  upon  sodium,  but  when  it  is  heated  with  potas- 
sium an  explosive  combination  takes  place. 

Experiment  125. — Upon  0.25  g.  of  pulverized  I,  placed  in  a  porcelain 
capsule,  pour  enough  strong  ammonia  water  to  cover  it  and  allow  it  to 
stand  for  15  or  20  minutes.  At  the  end  of  that  time,  stir  up  the  powder 
at  the  bottom  of  the  liquid  and  pour  a  quarter  of  the  contents  of  the 
capsule  upon  each  of  four  small  filters  (App.  8).  Wash  the  powder 
well  with  cold  H3O,  and  then  remove  the  filters  with  their  contents 
from  their  funnels.  Pin  the  niters  to  pieces  of  board  and  allow  them 
to  dry  without  heating.  When  the  powder  is  dry,  it  may  be  exploded 
by  brushing  it  with  a  feather  or  by  jarring  it  with  a  blow  upon  the 
table.  The  powder  is  nitrogen  iodide. 

119.  Nitrogen  Iodide.— Nitrogen  iodide  is  much 
less  explosive  than  nitrogen  chloride  (§  113)  but  it  should 
not  be  prepared  by  the  pupil  except  in  very  small  quanti- 
ties. Nitrogen  forms  a  similar  compound  with  bromine. 


LUORINE  ;  symbol,  F ;  atomic  weight,  19  m.  c. ;  quantimleme,  1. 

120.  Source.— Fluorine  occurs  in  nature  in  fluor  spar 
(calcium  fluoride,  CaF2),  and  in  cryolite  (sodium  and  alu- 
minum fluorides,  3NaF  -f  AIF3).    It  has  also  been  found  in 
minute  quantities  in  the  teeth,  bones  and  blood  of  animals. 

Note.—  Fluor  spar  is  a  mineral  found  somewhat  abundantly  in 
various  parts  of  the  world,  especially  in  Derbyshire  and  Cornwall, 
England.  Cryolite  is  found  in  large  quantities  in  Greenland. 

121.  Properties.— Fluorine   is  a  very  remarkable 
element  in  that  it  is  the  only  one  that  forms  no  compound 


§  121  FLUORINE.  101 

with  oxygen  and  that  it  has,  so  far,  resisted  all  of  the 
attempts  made  to  obtain  it  in  the  free  state.  When  set  free 
from  one  compound,  it  attacks  the  substance  nearest  at 
hand  to  form  a  new  compound.  It  surpasses  chlorine  in 
its  power  of  combining  with  hydrogen  and  the  metals,  and 
has  a  remarkable  tendency  to  .ccxmbine,  with  silicon^  The 
difficulties  in  the  way  of  its  prepaia'tionSin-d  collection  have 
prevented  its  satisfactory  study  by  chemists: «  Cp  frequently? 
but  little  is  known  concerning  *  ireje  fluorine1.  Its  com- 
pounds closely  resemble  those  of  chlorine,  bromine  and 
iodine. 

Note.  —  F  has  been  considered  subsequently  to  Cl,  Br  and  I, 
because  of  the  comparative  lack  of  knowledge  concerning  it.  There 
are  good  reasons  why,  in  grouping  them,  F  should  precede  Cl,  Br 
and  I. 

Experiment  126. — Rub  a  heated  piece  of  glass  with  beeswax.  If 
the  glass  be  hot  enough  to  melt  the  wax,  it  may  easily  have  one  of 
its  surfaces  covered  with  a  thin  layer  of  nearly  uniform  thickness. 
Let  the  glass  cool.  With  any  pointed  instrument,  write  a  name  or 
draw  a  design,  being  careful  that  every  stroke  cuts  through  the  wax 
and  exposes  the  glass  below.  In  a  small  tray  made  of  lead  (platinum 
is  better,  but  a  saucer  that  you  are  willing  to  spoil  will  answer),  mix 
a  spoonful  of  powdered  fluor  spar  or  cryolite  with  enough  H2S04  to 
make  a  thin  paste.  Place  the  prepared  glass  (waxed  side  down)  over 
the  tray  ;  heat  the  tray  gently  (not  enough  to  melt  the  wax)  and  set 
it  aside  in  a  warm  place  for  two  or  three  hours.  (Do  not  inhale  the 
acid  fumes.)  Clean  the  glass  by  scraping  it  and  rubbing  with  turpen- 
tine. The  name  or  design  will  be  seen  etched  upon  the  glass. 

Experiment  127. — Upon  a  pane  of  glass  that  will  fit  the  window  of 
your  chemical  laboratory,  or  the  glass  front  of  one  of  your  laboratory 
cases,  etch  the  proper  designation  of  the  class,  the  date,  and  the 
autographs  of  the  individual  members  of  the  class.  The  "  class 
artist "  may  add  an  appropriate  border  and  emblematic  designs,  ad 
libitum. 

Experiment  128. — Coat  the  convex  surface  of  a  watch  glass  with 
wax,  write  a  name  upon  it,  place  it  upon  a  small  lead  saucer  contain- 


102  THE    HALOGEN    GROUP.  §  122 

ing  mixed  CaF3  and  H2S04,  fill  the  watch  glass  with  H20  to  keep 
the  wax  from  melting,  and  hold  the  saucer  in  the  lamp  flame.  The 
etching  will  be  finished  in  a  few  minutes. 

122.  Hydrofluoric  Acid.— This  acid  (HF)  is  dis- 
tinguished from  all  other  substances  by  its  power  of  cor- 
roding glass.     It  evidently  corresponds  closely  to  the  other 
hydrides  of  this  .group'.  (t&  HCI,  HBr  and  HI)  but  it  is 
more  .enorgetic  than,  any  of  them.     It  is  readily  prepared, 

as  above,  by  distilling  soiwe  fluoride  with  sulphuric  acid,  e.g., 
CaF2  +  H2S04  =  CaS04  +  2HF. 

(a.)  The  reaction  is  closely  analogous  to  that  for  the  distillation  of 
NaCI  with  H2S04  (§  105,  a).  The  solution  of  HF  is  also  used  for 
etching  glass.  HF,  when  dry,  does  not  act  on  glass,  but  the  slightest 
trace  of  H20  renders  it  capable  of  doing  so. 

123.  The   Halogen  Group.— Fluorine,  chlorine, 
bromine  and  iodine  constitute  one  of  the  most  clearly 
defined  and  most  remarkable  natural  groups  known   to 
chemistry.     They  exhibit  a  marked  gradation  in  proper- 
ties and  close  analogies  in  their  elementary  condition  and 
in  their  corresponding  compounds. 

(a.)  Concerning  their  gradation  of  properties : 

1.  At  the  ordinary  temperature,  F  is  a  gas;  Cl  is  a  gas;  Br  is  a 
liquid  and  I  is  a  solid. 

2.  Liquid  Cl  is  transparent ;  Br  is  but  slightly  so ;  I  is  opaque. 

3.  C I  has  a  specific  gravity  of  35.5  ;  Br  vapor,  80  ;  I  vapor,  127. 

4.  F  has  an  atomic  weight  of  19  m.  c. ;  Cl,  35.5  m.  c  ;  Br,  80  m.  c. ; 
I,  127  m.  c, 

5.  Generally  speaking,  their  chemical  activities  are  graded  in  the 
inverse  order,  being  greatest  in  the  case  of  F  ;  less  in  Cl ;  still  less 
in  Br  and  least  in  I.     (In  the  case  of  such  natural  groups  the  chemi- 
cal activities  frequently  vary  inversely  as  the  atomic  weights.)    The 
atomic  weight  of    Br  is    nearly  the    mean  of  those  of   Cl   and  I 
(35.5  +  127  _  81.25)  and,  in  general  chemical  deportment,  Br  stands 
half  way  between  the  other  two  elements. 

(&.)  Concerning  their  analogies  : 

1.  Their  binary  compounds  with  potassium  and  sodium  resemble 


§  123  THE    HALOGEN    GROUP.  103 

sea  salt.     Hence,  these  compounds  are  called  haloid  salts  and  their 
elements,  halogens  (Greek,  halos,  salt  and  gennao,  I  produce). 

2.  Each  of  them  combines  with  H,  equal  volumes  of  the  constitu- 
ent gases  uniting  without  condensation,  to  form  the  haloid  acids, 
HF,  HCI,  HBrand  HI. 

3.  These  haloid  acids  all  have  a  great  attraction  for  H20  forming 
aqueous  solutions  that  have  the  same  chemical  properties  as  the 
acids  themselves. 

EXERCISES. 

1.  Give  two  of  the  most  marked  physical  properties  of  H,  and  two 
of  its  distinctive  chemical  properties. 

2.  What  is  a  triad ?    A  pentad?    A  quadrivalent  atom ?    A  biva- 
lent compound  radical  ?    Illustrate  each. 

8.  By  passing  the  vapor  of  I  with  H  over  platinum  sponge  heated 
to  redness,  a  strongly  acid  gas  is  synthetically  formed.  What  is  its 
name,  its  molecular  weight  and  its  specific  gravity  ? 

4.  A  large  jar,  about  a  quarter  full  of  chloride  of  Ihne  had  been 
standing  for  some  time  until  the  upper  part  contained  a  gas  given 
off  by  the  chloride.    Into  this  gas,  a  moistened  slip  of  paper  was 
thrust.    The  paper  was  instantly  colored  deep  blue.    What  was  the 
gas  and  with  what  was  the  test  paper  moistened  ?    Explain  the 
phenomenon. 

5.  What  analogies  exist  between  members  of  the  Halogen  group  ? 

6.  Symbolize  the  chlorides,  bromides,  iodides,  chlorates,  bromates 
and  iodates  of  the  following:  K',  Na',  Ag',  Cu",  Zn",  Au'",  Ptiv, 


STOICHIOMETRY. 


124.  Reactions  and  Reagents.  —  Any  change 
in  the  composition  of  a  molecule  is  called  a  chemi- 
cal reaction.    Substances  acting  in  such  a  chemical 
change  are  called   reagents. 

(a.)  Changes  in  molecular  composition  are  of  three  kinds : 

1.  Changes  in  the  kind  of  the  constituent  atoms. 

2.  Changes  in  the  number  of  the  constituent  atoms. 

3.  Changes  in  the  relative  positions  of  the  constituent  atoms. 

(6.)  When  H  burns  in  air,  the  H  and  0  react  upon  each  other  ;  they 
are  the  reagents  used  to  produce  a  molecular  change. 

125.  Expression  of  Reactions.— In   any  given 
substance  of  homogeneous  composition,  the  molecules  are 
all  alike.    The  nature  of  the  mass  depends  upon  the  nature 
of  the  molecule.     The  mass  may  be  fittingly  represented 
by  the  molecule.    Any  chemical  change  in  the  mass  may 
be  represented  by  a  corresponding  change  in  the  molecule. 
Hence,  chemical  reactions   are  generally  expressed 
in  molecular  symbols. 

126.  Factors  and  Products.  —  TJie  molecules 
that  go  into   a   reaction   are   called  factors;     the 
•molecules  that  come  from  it  are  called  products. 

(a.}  In  the  preparation  of  H  (§  23),  the  factors  were  Zn  »nd  2HCI  ; 
the  products  were  ZnCI8  and  H2. 


§  128  GRAVIMETRIC    COMPUTATIONS.  105 

127.  Chemical   Equations.  —  Chemical  reac- 
tions are  very  commonly  and  conveniently  repre- 
sented   Inj    equations,    placing    the    sum   of  the 
factors  equal  to  the  sum  of  the  products. 

(a.)  The  equality  results  from  the  indestructibility  of  matter 
(Ph.,  §  37).  It  indicates  that  the  number  of  each  kind  of  atoms  in 
the  products  is  equal  to  the  number  of  the  same  kind  of  atoms  in 
the  factors.  The  atoms  are  differently  arranged  but  not  a  single  one 
is  gained  or  lost.  From  this  it  follows  that  the  symbols  in  the  two 
members  of  the  equation  represent  the  same  number  of  microcriths. 
The  chemical  change  does  not  effect  any  change  in  weight.  (See 
Exp.  9.) 

(b.)  Re-examine  the  equations  already  given,  showing  their  agree- 
ment or  disagreement  with  the  above  statements. 

(c.)  The  equation  also  represents  the  relative  weights  of  the  several 
substances  engaged  in  the  reaction*  The  equation  H2  +  0  =  HZ0 
means,  literally,  that  2  m.  c.  of  H  united  with  16  m.  c.  of  0 
yields  18  m.  c.  of  H20,  but  the  relation  is  equally  true  for  larger 
quantities  of  matter.  Thus  we  may  learn  from  it  that  2  g.  of  H 
unites  with  16  g.  of  0  to  form  18  g.  of  H20,  or  that  12  Kg.  of  H 
unites  with  96  Kg.  of  0  to  form  108  Kg.  of  H20. 

(d.)  Strictly  speaking,  it  is  not  proper  to  represent  a  fractional 
part  of  a  molecule  as  entering  into  or  resulting  from  a  chemical  reac- 
tion, as  we  do  when  we  write  H2  +  0:=H30.  To  obviate  the  error 
of  representing  an  atom  of  free  0,  we  should  indicate  twice  the 
quantity  of  each  substance,  as  follows:  2H2  +  02  =  2H20.  ~Bat,for 
the  sake  of  convenience,  chemists  generally,  write  the  equations  in  the 
simpler  form,  as  the  gravimetric  relations  expressed  are  the  same. 

(e.)  The  equation,  written  in  complete  molecules,  also  represents 
volumetric  relations.  Remembering  Ampere's  law  (§  61),  we  easily 
see  that  2Ha  +  02  =  2H20  indicates  that  two  (molecular  or  other) 
volumes  of  H  unite  with  one  of  O  to  yield  two  volumes  of  dry  steam, 
e.  g.,  2  I.  of  H  and  1  I.  of  O  unite  to  form  2  I.  of  dry  steam. 

128.  Gravimetric  Computations.  —  Knowing 
the  equation  for  any  given  reaction  and  the  atomic  weights 
of  the  several  elements  involved,  we  are  able  to  solve  a 
great  many  problems  concerning  the  weight  of  substances 


106  VOLUMETRIC  COMPUTATIONS.  §  128 

appearing  as  factors  or  products.  From  the  data  now 
known  and  those  given  in  the  problem,  make  the  follow- 
ing proportion : 

As  the  number  of  microcriths  of  the  given  sub- 
stance is  to  the  number  of  microcriths  of  the  re- 
quired substance  so  is  the  actual  weight  of  the 
given  substance  to  the  actual  weight  of  the  re- 
quired substance. 

(a.)  The  number  of  microcriths  is  to  be  taken,  of  course,  from  the 
equation.  A  few  examples  are  given  : 

1.  How  much  H  can  be  obtained  from  HCI  by  using  20  g.  of  Zn 
(zinc)  ? 

Solution. — Write  the  reaction  with  the  molecular  weights  of  the 
several  reagents. 

2(1  +  35.5)    65  +  71 
Zn  +  2HC!  •=  ZnCI2  +  H2. 
65  m.  c.  73  m.  c.     136  m.  c.   2  m.  c. 

Form  the  proportion  according  to  the  above  rule : 

65  m.  c.  :  2  m.  c.  :  :  20  g.   :  x  g. 

.-.  x  =  0.61538  g.  or  615.38  mg.  of  H.— Ans. 

2.  How  much  HCI  will  be  required? 

65  wi.  c. :  73  m.  c. : :  20  g. :  x  g. 

.-.  x  =  22.46  g.  of  dry  HCI.— 4w*. 

3.  How  much  ZnCI2  will  be  produced? 

65  m.  c. :  136  m.  c.i:  20  g. :  x  g. 

.-.  x  =  41.846  £.  of  ZnClo.—  Ans. 

4.  How  much  Zn  is  necessary  to  prepare  1  El  of  H  ? 

As  one  liter  of  H  weighs  1  crith  or  .0896  g.,  1000  I.  weighs  89.6  g. 
65  m.  c.:2m.c.::  x  g.  :  89.6  g. 

.'.  x  —  2912  g.  or  2.912  Kg.  of  Zn.— Ans. 

129.  Volumetric  Computations. — Every  equa- 
tion written  in  the  molecular  symbols  of  aeriform  sub- 
stances maybe  read  by  volume.  For  example  2H2-f02 
=  2H20  may  be  read :  two  volumes  of  hydrogen  unite 


§  130  PERCENTAGE   COMPOSITION.  107 

with  one  volume  of  oxygen  to  form  two  volumes  of  dry 
steam.     We  give  a  few  examples. 
(a.)  1.  How  much  steam  is  formed  by  the  combustion  of  1 1.  of  H  ? 

Solution.— ~By  referring  to  our  equation,  we  see  that  the  volumes 
of  H  and  of  H20  are  equal,  because  it  shows  an  equal  number  of 
molecules  for  those  substances,  and  we  know,  from  Ampere's  law. 
that  equal  numbers  of  gaseous  molecules  will  occupy  equal  volumes. 
Hence,  the  combustion  of  1  L  of  H  will  give  1  I.  of  dry  steam. 

2.  How  much  0  is  needed  to  burn  up  500  cu.  cm.  of  H  ? 

Solution. — The  equation  for  the  combustion  of  H  shows  that  the 
volume  of  0  is  half  that  of  the  H .  Hence,  it  will  require  half  of 
500  cu.  cm.  or  250  cu.  cm.  of  0. 

3.  How  much  H  must  be  burned  to  form  4  I.  of  steam  ? 

Solution. — The  equation  shows  a  relation  of  equality  between 
the  volumes  of  H  and  of  H20  (as  in  the  first  example).  Conse- 
quently, 4  1.  of  steam  requires  4  I.  of  H. 

4.  How  much  0  can  be  obtained  from  the  electrolysis  of  3  I.  of 
steam  ? 

Solution. — The  equation  shows  that  the  volume  of  0  is  half  that 
of  aeriform  H  80.  Hence,  3 1.  of  steam  will  yield  1.5  I.  or  1500  cu.  cm. 
of  O. 

13O.  Percentage  Composition.  —  The  method 
of  solving  problems  of  this  kind  will  be  illustrated  by  ex- 
amples, as  follows : 

(1.)  What  is  the  percentage  composition  of  HN03  ? 

Solution.— The  molecular  weight  of  HN03  is  1  m.  c.  +  14m.  e. 
+  48  m.  c.  —  63  m.  c. 

63  m.  c.  :   1  m.  c. : :  100%  :  (  1.59%,  the  proportion  of  H. 
63  m.  c. :  14  m.  c. : :  100%  :  &2.22%,  "         "        N, 

63  m.  c.  :4Sm.c.::  100%  :  76.19%  "         "        O. 

100.00%  * 

(2.)  The  vapor  density  of  a  certain  compound  is  14.  Analysis 
shows  that  85.7%  of  it  is  O  and  14.3%  is  H.  What  is  its  symbol? 


108  PERCENTAGE    COMPOSITION.  §  130 

Solution. — If  its  vapor  density  is  14,  its  molecular  weight  is  28  m.  c. 
(%  63). 

100$  :  85.7/c  : :  28  m.  c. :  24  m.  c.  =  C2. 

100$  :  14.3$  : :  28  m,  c. :    4  m.  c.  —  H4  or  2H2. 

Therefore,  the  symbol  is  C2H4. 

Note. — Gaseous  volumes  will  vary  witli  pressure  (Ph.,  §  284)  and 
temperature  (Ph.,  §  492).  In  comparing  such  volumes,  measured 
under  different  conditions,  the  proper  correction  must  be  made  for 
this  variation  (Ph.,  §  494).  It  is  common  to  refer  gaseous  volumes 
to  a  temperature  of  0°C.  and  a  pressure  of  760  mm.  The  branch  of 
chemistry  that  deals  with  the  numerical  relations  of  atoms  is  called 
stoichiometry.  The  gravimetric  and  volumetric  and  percentage 
computations  above  are  stoichiometrical  computations. 

EXERCISES. 

1.  What  do  atomic  weights  express?    What  weight  of  0  can  be 
obtained  by  decomposing  9  g.  of  steam  ? 

2.  Give  the  law  of  multiple  proportions,  and  illustrate  it  by  the 
compounds  of  N  and  0. 

3.  Find  the  percentage  composition  of  H2S04. 

4.  Upon  heating  potassium  dichromate(K2Cr207)  with  a  sufficient 
quantity  of  HCI,  one  may  obtain   Cr2CI6  +  2KCI   and  water  and 
chlorine.    Write  the  reaction. 

5.  (a.)  How  much  Zn  is  needed  to  obtain  20  g.  of  H  ?    (&.)  How 
much,  if  the  Zn  contains  5  per  cent,  impurities  ?  ^7  t$jtri&-" 

6.  (a.)  How  much  0  would  be  necessary  to  burn "500  cu.  cm.  of  H  ? 
(&.)  If  the  experiment  were  performed  in  an  atmosphere  at  a  tempera- , 
ture  of  100°C.,  what  would  be  the  name  and  volume  of  the  product  ? 
(c.)  How  much  would  be  necessary  to  burn  5  g.  of  H  ? 

7.  (a.)  What  liquid  is  used  in  the  preparation  of  HCI?    (&.)  What 
is  the  greatest  amount  of  HCI  that  can  be  prepared  by  using  196  g. 
of  that  liquid  ?    .'     .'jt,^ 

8.  (a.)  What  is  the  difference  between  hydrochloric  acid  and  muri- 
atic acid  ?    (&.)  What  is  aqua  regia?    (c.)  Name  ^and  symbolize  the 
five  oxides  of  N. 

9.  (a.)  Explain  the  difference  between  a  bivalent  and  an  univalent 
metal.     (6.)  What  is.  quanti valence? 

10.  When  HI  gas  is  passed  through  a  heated  glass  tube,  it  is  de- 
composed, and  a  violet  color  appears.    Account  for  the  appearance 
of  the  color. 


§  130  PERCENTAGE    COMPOSITION.  109 

11.  The  reaction  of  Cl  upon  NH3  is  as  follows  : 
8NH8  +  3CI8  =  Na  +6NH4CI. 


(a.)  What  weight  of  Cl  is  necessary  to  the  production  of  12.544 g. 
of  N  ?    (&.)  What  volume  of  Cl  ? 

12.  Marsh  gas  is  8  times  as  heavy  as  H.     Analysis  shows  that  f  of 
its  weight  is  C  and  the  rest  H.     The  atomic  weight  of  C  is  12  m.  c. 
What  is  the  symbol  for  marsh  gas  ? 

13.  What  is  the  normal  volume  of  a  quantity  of  0  that  measures 
1 1.  at  a  barometric  reading  of  756  mm.9.     (Ph.,  §  494.) 

*»     I  1>N  ^' 

*'# 


' 


THE    SULPHUR    GROU  P. 


i. 


SULPHUR. 


$3JT  'Symbol,  S  ;  specific  gravity,  1.9G  to  2.07  ;  atomic  weight,  32  m.c.  ; 
molecular  weight,  at  1000'  'C.,  64  m.  c.  ;  quantivalence,  2  (4  or  6). 

131.  Occurrence.  —  Both  free  and  combined  sulphur 
are  found  in  nature.  Free  sulphur  is  found  in  certain 
volcanic  regions,  especially  Sicily,  occurring  sometimes  in 
the  form  of  transparent  yellow  crystals,  called  "  virgin  sul- 
phur/' but  generally  mixed  with  earthy  materials.*  It  is 
found  in  combination  with  hydrogen  or  with  the  metals, 
as  sulphides  ;  and  with  oxygen  and  many  metals,  as  sul- 
phates. 

(a.)  Among  the  native  sulphides,  we  may  mention  hydrogen  sul- 
phide (sulphuretted  hydrogen,  H2S),  a  gaseous  constituent  of  the 
waters  of  "sulphur  springs";  lead  sulphide  (galena,  PbS);  zinc  sul- 
phide (blende,  ZnS)  ;  copper  sulphide  (chalcocite,  CuS)  and  iron  disul- 
phide  (pyrite,  FeS2),  etc. 

(&.)  Among  the  native  sulphates  we  may  mention  calcium  sulphate 
(gypsum,  CaS04)  ;  barium  sulphate  (barite  or  heavy  spar,  BaS04) 
and  sodium  sulphate  (Glauber  salt,  Na2S04). 

(c.)  S  is  found  in  animal  and  vegetable  tissues. 

(d.)  Nearly  all  of  the  S  of  commerce  comes  from  Sicily.  Some  of 
the  native  crystals  here  found  are  5  or  7  cm.  in  diameter. 


132 


SULPHUR. 


Ill 


133.  Preparation.— Native  sulphur  is  freed  from 
most  of  its  earthy  impurities  near  the  place  where  it  is 
found  and  thus  fitted  for  purposes  of  commerce.  The 
process  is  one  of  fusion  or  of  distillation.  Sulphur  is  also 
obtained  from  pyrite  by  heat. 

(a.)  One  method  of  obtaining  crude  sulphur  from  the  native  earthy 


FIG.  56. 

material  is  represented  in  Fig.  56.  The  earthy  material  is  heated  in 
earthenware  pots,  a  a  ;  the  vaporized  S  passes  over  into  the  similar 
pots,  6  6,  placed. outside  the  furnace.  The  S  vapor  here  condenses  to 
a  liquid  and  then  runs  out  into  wooden  vessels  partly  filled  with 
H20.  It  is  said  that  this  process  is  unknown  in  Sicily. 

(6.)  When  the  earth  is  very  rich  in  S,  it  is  sometimes  heated  in 
large  kettles.  The  S  melts  and  the  earthy  matter  settles  to  the  bot- 
tom, leaving  the  liquid  S  to  be  dipped  out  from  above.  Sometimes 
the  earth  is  piled  up  in  a  heap  and  heated,  the  heat  coming  from  the 
combustion  of  a  part  of  the  S  or  of  other  fuel  previously  added  in 
proper  quantity.  The  melted  S  flows,  from  the  heap  or  settles  into  a 
cavity  at  the  bottom.  In  this  latter  process,  which  is  largely  used 
in  Sicily,  two  thirds  of  the  S  is  lost  by  its  combustion. 

(c.)  Pyrite  (iron  pyrites,  FeS2)  is. sometimes  piled  up  with  fuel, 
which  is  then  ignited.  The  heat  frees  part  of  the  S  of  the  FeS2  and 
melts  it.  The  melted  S  settles  into  cavities  provided  for  that  pur- 
pose. 


112 


SULPHUR. 


132 


(d.)  The  crude  S,  provided  by  the  foregoing  processes,  is  then 
further  purified  by  distillation.     It  is  melted  in  a  tank,  a,  runs 


FIG.    57- 

through  a  pipe  into  the  iron  retort,  &,  where  it  is  vaporized.  The 
vapor  passes  from  &  into  the  large  brick  chamber,  C,  where  it  con- 
denses. When  the  walls  of  C  are  cold,  the  S  condenses  in  the  form 
of  a  light  powder  known  as  "  flowers  of  sulphur  "  ;  when  the  walls 
of  C  are  hot,  the  S  condenses  to  a  liquid,  and  collects  on  the  floor  of 
the  chamber,  whence  it  is  drawn  off  and  run  into  moulds  to  form 
"  roll  brimstone." 

Experiment  129. — Put  30  g.  of  small  pieces  of  S  into  a  test  tube  of 
30  cu.  cm .  capacity.  Hold  the  test  tube  in  the  lamp  flame .  Notice  that 
it  melts,  forming  a  limpid  liquid  of  light  yellow  color.  Heat  it  hot- 
ter and  notice  that  it  becomes  viscid  and  dark  colored.  Heat  it  hotter 
and  notice  that  it  becomes  almost  black.  Invert  the  test  tube  and 
notice  that  the  S  has  become  so  viscid  that  it  will  not  run  out  from 
the  tube.  Heat  it  hotter  and  notice  that  it  again  becomes  fluid. 
Heat  it  until  it  boils  and  notice  that  it  is  converted  into  a  light  yel- 
low vapor. 

Experiment  130.— Pour  half  of  the  boiling  S  of  the  last  experi- 


132 


SULPHUR. 


113 


ment,  in  a  fine  stream,  into  a  large  vessel  nearly  full  of  cold  H20. 
The  S  when  taken  from  the  H20  will  be 
found  to  have  no  crystalline  structure,  to  be 
soft,  nearly  black  and  plastic.  Allow  the  S 
remaining  in  the  test  tube  to  cool  slowly  and 
quietly,  under  close  observation.  Notice  that 
it  repasses  through  the  viscid  and  limpid 
states  and  finally  solidifies  with  a  crystalline 
structure.  The  needle  like  crystals  may  be 
seen  shooting  out  from  the  cooling  walls  of 
the  tube  into  the  liquid. 

Experiment  m— Melt  200 
Hessian  crucible.  Allow  it  to 
cool  until  a  crust  forms  over 
the  top.  Through  a  hole 
pierced  in  this  crust,  pour  out 
the  remaining  liquid  S.  When 
the  crucible  is  cool,  break  it 
open.  It  will  be  found  lined 
FIG.  58.  with  needle  shaped  crystals. 

crucible  may  be  spared  by  pouring  all  of  the  melted  S 

into  a  pasteboard  box  or  other  convenient  receptacle  and  securing 

the  formation  of  the  crystals  there. 
Experiment  132. — Dissolve  a  piece  of  S  in  carbon  disulphide  (CS2). 

The  CS2  will  quickly  evaporate,  leaving  behind  crystals  of  S,  that 

resemble  the  native  crystals. 
Note.— The  many  forms  of  crystals  have  been  classified  into  six 

systems  of  crystallization : 

1.  Isometric — axes  equal. 


FIG.  59- 


2.  Tetragonal)  iateral axes  equal. 
8.  Hexagonal  ) 


4.  Orthorhombic ) 

5.  Monoclinic      >•  axes  unequal. 

6.  Triclinic          ) 

The  crystals  of  S  formed  by  fusion  (Exp.  131)  are  monoclinic  ;  the 
native  crystals  and  those  formed  by  solution  and  evaporation  are 
orthorhombic.  Substances  which,  like  S,  crystallize  under  two  sys- 
tems are  called  dimorphous  (two  formed).  Sulphur  is  not  only  thus 
dimorphus,  but  the  plastic  variety  (Exp.  130)  is  amorphous  (without 
crystalline  form).  Other  substances,  like  titanium  dioxide,  crystal- 
lize in  three  distinct  forms  and  are  said  to  be  trimorphous.  A  varia- 
tion in  crystalline  form  is  accompanied  by  differences  in  other  physi- 
cal properties,  as  specific  gravity,  hardness,  refractive  power,  etc. 
Different  substances  that  crystallize  in  the  same  form  are  said  to  be 
isomorphous.  Substances  that  exhibit  a  double  isomorphism  are  said 
to  be  isodimorphous.  The  trioxides  of  arsenic  and  antimony  are 
isodimorphous. 


114  SULPHUR.  §  133 

133.  Physical  Properties.  —  Sulphur  manifests 
remarkable  changes  when  heated.  It  melts  at  115°C.  ; 
becomes  dark  colored  and  viscid  at  230°C.;  regains  its 
fluidity  at  above  250°C.,  and  boils  at  450°C.  On  cooling, 
these  changes  occur  in  inverse  order.  The  specific  gravity 
of  its  vapor  at  500°C.  is  96,  but  at  1000°C.  it  is  32.  This 
seems  to  indicate  that  at  500°C.  the  molecule  is  composed 
of  six  atoms,  which  are  disassociated  at  a  higher  tempera- 
ture, so  that,  at  1000°C.,  the  molecule  is  composed  of  only 
two  atoms.  It  exists  in  three  distinct  forms,  orthorhombic, 
monoclinic  and  amorphous. 

(a.)  The  orthorhombic  or  natural  form  of  S  is  brittle  and  soluble  in 
carbon  disulphide,  petroleum  or  turpentine.  Its  specific  gravity  is  2.05. 
(6.)  The  monoclinic  form  is  brittle  and  unstable.  After  exposure 
to  the  air  for  several  days,  each  transparent,  needle  shaped  crystal  is 
converted  into  a  large  number  of  the  orthorhombic  or  permanent 
crystals,  thus  becoming  opaque.  Its  specific  gravity  is  1.96.  It  is 
formed  as  shown  in  Exp.  131. 

(c.)  The  amorphous  form  is  plastic  and  insoluble  in  CS2.  Exposed 
to  the  air,  it  gradually  assumes  the  ordinary  brittle  form  at  ordinary 
temperatures ;  heated  to  100°C.,  it  instantly  changes,  and  evolves 
enough  heat  to  raise  its  temperature  to  110°C.  Its  specific  gravity  is 
1.96.  It  is  formed  by  pouring  S,  heated  above  250°C.,  into  ^old  H20, 
as  shown  in  Fig.  58. 

Experiment  183. — Mix  intimately  4  g.  of 
flowers  of  S  and  8  g.  of  copper  filings. 
Heat  the  mixture  in  an  ignition  tube  (see 
Exp.  11)  until  the  elements  unite  with  a 
vivid  combustion  to  form  copper  sulphide 
(CuS). 

Experiment  134. — Burn  a  small  piece  of 
S  in  the  air  and  notice  the  peculiar  blue 
light  and  the  familiar  odor  of  the  suffocat- 
ing gaseous  product  (§  144). 


Chemical  Properties. 

— Sulphur  unites  with  oxygen  at  the 
FiG.~6o.  comparatively    low    temperature    of 


§  136  SULPHUR.  115 

about  250°C.     It  enters  energetically  into  union  with  most 
of  the  elements,  in  many  cases  with  the  evolution  of  light. 

135.  Uses.—  Sulphur  is  largely  used  in  the  manufac- 
ture of  sulphuric  acid,  vulcanized  india-rubber,  friction 
matches   and    gunpowder    and   in   bleaching  straw  and 
woolen  goods. 

136.  Tests.  —  Free  sulphur  is  easily  recognized  by  its 
color  and  by  its  odor  when  burned.   Combined  sulphur  may 
be  detected  by  mixing  the  compound  with  pure  sodium 
carbonate  and  fusing  the  mixture  before  the  blowpipe  on 
charcoal.      The   fused  mass    contains   sodium  sulphide. 
When  it  is  placed  on  a  silver  coin  and  water  added,  a  brown 
stain  of  silver  sulphide  is  formed  on  the  coin. 

Note.  —  Sulphides  were  formerly  called  sulphurets. 

^8i\  +  Pttf*>6* 
EXERCISES. 

r    1.  Why  are  the   ends  of  friction  matches  generally  dipped  in 
melted  S  ? 

2.  When  S    is  prepared  from  pyrite,  Fe3S4  is  formed.     Write  the 
reaction.      $>/£&.  -  Iffjr:*"*' 

^3.  By  bringing  Brand   P  together  in  the  presence  of  H20,  both 
*  phosphoric  (H  3  PO  4)  and  hydrobromic  acids  are  formed,     (a.)  What 
yj£  weight  of  Br  is  necessary  to  yield  5  g.  of  the  colorless  gas,  HBr? 
'   (&.)  What  weight  of  Br  is  necessary  to  yield  10  I.  of  HBr?  . 

4.  I  acts  upon  KCI03,  forming  potassium  iodate  and  setting  Cl 
free  : 

2KCI03  +  I3  =  2KI03  +  CI2. 


(a.)  How  much  Cl  by  weight  may  thus  be  freed  by  10  g.  of  I  ? 
(5.)  How  much  by  volume?   £  rfr/J 

.  (a.)  How  many  grams  of  H  may  be  prepared  by  the  use    of 
-  of  Zn?    (&.)  How  many  liters?     (c.)  How  many  grams  of  HCI 
are  necessary  ? 

6.  (a.)  If  20  g.  of  H  be  exploded  with  0,  how  many  grams  of  0  are 
necessary?    (&.)  How  many  grains  of  dry  steam  will  be  produced? 

7.  (a.)  1   cu.cm.   of  H20  will  yield,  by   electrolysis,  how  many 
grams  of  free  gases?    (&.)  How  many  cu.  cm.  of  0?    (c.)  How  many 


: 


116  SULPHUR.  §  136 

cu.  cm.  of   H  ?    (d.)   The  explosion  of  thes3  gases  will  yield  how 
many  cu.  cm.  of  dry  steam  ? 

8.  (a.)  If  ozone  could  be  produced  from  KCI03,  how  many  grams  of 
the  former  could  be  produced  from  10  g.  of  the  latter  ?    (6.)  How 
many  liters  of  the  former  ?  ; 

9.  (a.)  Is  gunpowder  manufacture  a  chemical  or  a  physical  pro- 
cess ?    Why  ?    (&.)  The  combustion  of  gunpowder  ?     Why  ? 

10.  Calomel  and  corrosive  sublimate  are  each  composed  of  Hg  and 
Cl  atoms.     Why  do  the  two  substances  differ,  their  atoms  being  of 
the  same  kind?  ftfy  :7  **f  (> 

11.  What  is  the  difference  between  organic  and  inorganic  matter  ? 

12.  State  two  peculiarities  of  chemical  affinity. 

13.  The  constituents  of  air  are  free.    Is  the  air  a  compound  ? 


138 


HYDROGEN    SULPHIDE. 


117 


HYDROGEN    SU  LPH  IDE. 

137.  Occurrence.  —  Hydrogen  sulphide  (hydrogen 
monosulphide,    sulphuretted    hydrogen,    hydrosulphuric 
acid,  H2S)  occurs  native  in  certain  volcanic  gases  and  is 
the  characteristic  constituent  of  the  waters  of  "sulphur 
springs."    It  is  generated  by  the  putrefaction  of  animal 
matter  and  causes  the  peculiar  odor  of  rotten  eggs. 

138.  Preparation.  —  Hydrogen  sulphide  may  be 
prepared  by  the  direct  union  of  its  constituents,  but  it  is 
generally  prepared  by  the  action  of  dilute  sulphuric  or 
hydrochloric  acid  upon  iron  sulphide  (ferrous  sulphide, 
FeS). 

(a.)  Into  a  gas  bottle,  arranged  as  for  the  preparation  of  H  (§  20), 
put  about  10  g.  of  FeS,  replace  the  cork  snugly,  add 
enough  H20  to  seal  the  lower  end  of  the  funnel  tube, 
and  place  the  bottle  out  of  doors,  or  in  a 
good  draft  of  air,  to  carry  off  any  of  the 
offensive  H  2S  that  may  escape.  Let  the  de- 
livery tube  dip  5  or  6  cm.  under  cold  H2O, 
contained  in  another  bottle,  e.  Add  a  few 
cu.  cm.  of  H2S04  or  HCI.  Bubbles  of  gas 
appear  in  e  and  are  absorbed  by  the  H20. 
Add  acid  in  small  quantities,  as  in  the 
preparation  of  H,  until  the  H20  ine  smells 
strongly  of  the  gas.  Remove  the  gas  bottle 
and  cork  tightly. 

FeS  +  H2S04  =  FeS04  +  H2S, 
or FeS  +  2HCI  =  FeCI2  +  H2S. 

(&.)  Fig.  63  represents  a  convenient  piece  of  apparatus  for  the 
preparation  of  H2S.  It  consists  of  three  bulbs  of  glass,  the  lower 
two,  &  and  c,  being  in  a  single  piece,  the  tubular  prolongation  of 
the  upper  one,  a,  being  ground  to  fit  gas  tight  into  the  neck  of  & 
at  I  and  extending  downward  nearly  to  the  bottom  of  c.  Lumps  of 


FIG.  61. 


118 


HYDROGEN  SULPHIDE. 


138 


FeS,  as  large  as  can  be  admitted  through  the  tubulure  at  m,  are  in- 
troduced into  b,  the  stricture  at  e,  sur- 
rounding the  prolongation  of  a,  pre- 
venting them  from  falling  into  c.  The 
tubulure  at  m  is  then  closed  by  a  cork 
carrying  a  glass  stop-cock.  The  dilute 
acid  (1  part  H2S04  +  14  parts  H20)is 
poured  in  through  the  safety  tube,  t, 
passes  into  c  and  rises  into  b,  covering 
the  FeS.  H2S  is  generated  in  5,  an? 
escapes  through  the  stop-cock  at  m. 
When  this  stop-cock  is  closed,  the  con- 
fined gas  presses  on  the  surface  of  the 
liquid  in  b  and  forces  it  into  c  and  a. 
When  the  acid  is  no  longer  in  contact 
with  the  FeS,  the  generation  of  H2S 
ceases,  and  the  gas  in  b  is  held,  under 
pressure,  ready  for  use.  The  acid  may 
be  removed  from  the  apparatus  by  the 
tubulure  at  n,  when  it  is  necessary  to 
renew  it. 


FIG.  62. 


(0.)    Argand    lamp    chimneys   fre- 
quently break  at  the  neck  near  the 
bottom.    Into  such  a  broken  chimney, 
put  a  glass  ball  of  such   size  that  it  will   not  pass  through  the 
stricture.      Support  the  chimney  by  a  perforated  cork,  in  a  vessel 

containing  dilute  acid  and  pro- 
vide a  delivery  tube,  as  shown  in 
Fig.  63.  Place  lumps  of  FeS  in 
the  chimney  above  the  glass  ball, 
replace  the  cork  with  the  de- 
livery tube,  push  the  chimney 
down  through  the  large  cork 
into  the  acid  ;  the  generation  of 
H2S  begins.  When  the  reaction 
has  continued  as  long  as  desired, 
lift  the  chimney  out  of  the  acid 
by  sliding  it  up  through  the 

large  cork.  Any  member  of  the  class  can  make  this  piece  of  appa- 
ratus, which  is  very  convenient  when  only  a  small  quantity  of  H2S  is 
wanted  at  a  time.  Of  course,  it  is  not  necessary  that  the  argand 
lamp  chimney  be  broken.  In  the  figure,  the  open  vessel  is  supposed 
to  contain  ammonia  water,  to  retain  the  H3S  that  may  escape  solu- 
tion in  the  H80  of  the  middle  bottle. 


139 


HYDROGEN    SULPHIDE. 


119 


(d.)  If  desirable,  the  gas  may  be  collected  over  warm  H20. 

(e.)  H2S  may  be  prepared  by  heating  a  mixture  of  equal  parts  of  S 
and  paraffiu.  By  regulating  the  temperature,  the  evolution  of  H3S 
niay  be  controlled.  When  the  mixture  is  allowed  to  cool,  the  evolu- 
tion of  the  gas  ceases  ;  when  the  mixture  is  again  heated,  H2S  is 
again  given  off.  This  is  a  very  convenient  method  of  preparing  H2S, 
but,  it  is  said,  that  it  sometimes  leads  to  explosions.  The  chemical 
changes  involved  in  the  process  are  still  obscure. 

139,  Physical  Properties.  —  Hydrogen  sulphide 
is  a  colorless  gas,  having  a  sweetish  taste  and  the  offensive 
odor  of  rotten  eggs.  It  may  be  liquefied  and  solidified  by 
cold  and  pressure.  Its  specific  gravity  is  17,  it  being,  thus, 
a  little  heavier  than  air.  At  ordinary  temperatures,  water 
dissolves  a  little  more  than  three  times  its  volume  of  the 
gas.  The  solution  has  the  peculiar  odor  of  the  gas  and  a 
slightly  acid  reaction. 

Experiment  135. — Bring  a  flame  to  the  open  mouth  of  ajar  of  H2S. 
The  gas  will  burn  with  a  pale  blue  flame,  forming  H30  and  S02  and 
depositing  a  slight  incrustation  of  S  on  the  inside  of  the  jar. 

Experiment  136.— Fill  a  Volta's  pistol  [Ph.,  §  371 
(35)]  with  a  mixture  composed  of  three  volumes  of 
0  and  two  volumes  of  H3S.  Pass  an  electric  spark 
from  the  electric  machine  or  induction  coil  through 
the  mixed  gases.  They  will  explode  violently,  com- 
plete combustion  taking  place. 

Experiment  137.— Attach, 
a  drying  tubs,  containing 
calcium  chloride,  to  the 
delivery  tube  of  the  gas 
bottle.  Provide  the  dry- 
glass  tubing.  When  all 
from  the  apparatus,  and 
match  to  the  jet.  (A  mix- 
plosive.)  The  gas  will 
Hold  a  dry  bottle  over  the 
dense  on  the  sides  of  the 
den  blue  litmus  paper. 


ing  tube  with  a  jet  made  of 
of  the  air  has  been  expelled 
not  till  then,  hold  a  lighted 
ture  of  H2S  and  air  is  ex- 
burn  with    a    blue   flame, 
flame.     Moisture  will   con- 
bottle.   This  liquid  will  red- 
H2S  +  302  =  2H00  + 
2S0, 


FIG.  64. 


120 


N TDK  0  G  EN    S  ULPHIDE. 


§139 


Experiment  138.— Burn  a  jet  of  H2S,  using  the  apparatus  arranged 

as  described  in  Exp.  28. 
Test  the  liquid  that  accu- 
mulates in  the  bend  of  d 
with  blue  litmus  paper. 

Experiment  139.  —  Inter- 
pose a  glass  tube  between 
the  drying  tube  and  the  jet 
(Fig.  65).  Heat  this  tube. 
The  H2S  will  be  decom- 
posed and  the  S  be  deposited 
on  the  cold  part  of  the  tube. 
The  product  that  now  accu- 


FIG.  6s. 


mulates  in  the  bend  of  d  will  not  redden  blue  litmus  paper.     The 
analysis  of  H2S  is  here  followed  by  the  synthesis  of  H20. 

Experiment  1^0. — Fill  a  glass  cylinder  with  H2S  and  a  similar  one 
with  Cl.  Bring  the  cylinders  together,  mouth  to  mouth.  HCI  is 
formed  and  S  deposited. 

Experiment  14 /.—Let  a  few  drops  of  fuming  H  N03  fall  into  a  globe 
of  H2S.  The  gas  will  be  decomposed  with  an  explosion.  Try  the 
experiment  with  strong  H2S04  or  with  Nordhausen  acid  (§  156). 

Experiment  143. — Moisten  a  bright  silver  or  copper  coin  and  hold 
it  in  a  stream  of  H2S.  The  coin  will  be  quickly  blackened  by  the 
formation  of  a  metallic  sulphide.  The  same  effect  will  follow 
the  dipping  of  the  bright  coin  into  a  solution  of  H8S  in  H20  (sul- 
phuretted hydrogen  water).  See  §  138,  a. 

Experiment  143. — Write  your  name  in  a  colorless,  aqueous  solu- 
tion of  lead  acetate  (sugar  of  lead).  Hold  the  autograph,  before  dry- 
ing, in  a  stream  of  H2S.  The  lead  sulphide  formed  renders  the  in- 
visible writing  legible. 

Experiment  144. — Make  a  sketch  in  the  same  colorless  liquid  and 
allow  it  to  dry.  At  any  convenient  time,  float  the  paper  containing 
the  invisible  design  upon  H2S  water.  The  figure  will  "come  out" 
promptly. 

Experiment  145.  —  Connect  five  bottles,  as  shown  in  Fig.  66. 
Put  a  dilute  solution  of  lead  acetate  or  nitrate  into  a  :  an  acid  solu- 
tion of  arsenic  into  & ;  one  of  antimony  into  c ;  a  dilute  solution  of 
zinc  sulphate,  to  which  a  little  NH4HO  has  been  added,  into  d; 


§  141  HYDROGEN   SULPHIDE.  121 

NH4HO  into  e.     Pass  a  current  of  H2S  from  tlie  generator  through 
the  bottles.    A  black  lead  sulphide 
will  be  precipitated  in  a ;  yellow  ar- 
senic sulphide,  in  & ;    orange   anti- 
mony sulphide,  in  c  ;  white  zinc  sul- 
phide, in  d.    The  zinc  sulphide  is    _s, 
soluble  in  dilute  acids.    The  NH3  was   % 
added  to  the  contents  of  d  to  destroy 
the  acidity  of  the  solution,  to  the  end 
that  the  sulphide  might  be  precipitated, 

140.  Chemical  Properties.— Hydrogen  sulphide 
is  easily  combustible,  the  products  of  its  combustion  being 
water  and  sulphur  dioxide  (§  144).     It  is  readily  decom- 
posed by  heat  and  by  certain  metals  in  the  presence  of 
moisture  and  by  many  oxidizing  agents.     It  precipitates 
metallic  sulphides  from  .solutions  of  the  compounds  of 
many  metals.    It  may  be  liquefied  by  cold  and  pressure. 
Its  solution  reddens  blue  litmus.    The  gas  is  very  poison- 
ous when   breathed,  and  even  when  much  diluted  its 
respiration  is  very  injurious.     Under  such  circumstances, 
the  best  antidote  is  the  inhalation  of  very  dilute  chlorine 
obtained  by  wetting  a  towel  with  dilute  acetic  acid  and 
sprinkling  over  it  a  few  decigrams  or  grains  of  bleaching 
powder. 

141.  Composition.— The  composition  of  hydrogen 
sulphide  may  be  ascertained  by  heating  metallic  tin  in  a 
known  volume  of  the  gas.     The  gas  will  be  decomposed, 
the  sulphur  combining  with  the  tin  as  tin  sulphide  and  the 
hydrogen  being  set  free.     The  volume  of  hydrogen  will  be 
the  same  as  that  of  the  hydrogen  sulphide  decomposed. 
When  a  platinum  wire  spiral  is  heated  red  hot  in  a  known 
volume  of  hydrogen  sulphide  by  the  passage  of  an  electric 
current  (Ph.,  §  387),  the  gas  is  decomposed,  both  of  its 

6 


122  HYDROGEN  SULPHIDE. 

constituents  being  set  free.  The  volume  of  the  hydrogen 
will  again  be  the  same  as  that  of  the  hydrogen  sulphide. 
Careful  analyses  have  proved  that  the  gravimetric  and 
volumetric  composition  of  this  gas  may  be  expressed  by 
the  following  diagram : 


ELS 

34  m.  c. 


(a.)  The  tJtree  atoms  in  the  molecule  of  H2S  occupy  the  same  vol- 
ume as  the  two  atoms  in  the  molecule  H2.  In  other  words,  molecular 
volumes  are  equal  (§  61). 

142.  Uses  and  Tests. — Hydrogen  sulphide  is  very 
extensively  used  in  the  chemical  laboratory  as  a  reagent, 
forming  sulphides  that  are  characteristic  (in  color,  solu- 
bility or  some  other  easily  recognized  property)  for  certain 
metals  or  groups  of  metals.  It  is  easily  detected  by  its 
odor  or  by  holding  in  it  a  strip  of  paper  wet  with  an  aque- 
ous solution  of  lead  acetate. 

Note. — Hydrogen  persulphide  (H2S2)  is  known  to  chemists.     It  is-- 
a  yellow,  transparent,  oily  liquid. 

'  EXERCISES. 

1.  Write  the  reaction  for  Exp.  135.  ^y  3  •*  W  : 

2.  When  metallic  tin  is  heated  in  H2S,  the  gas  is  decomposed. 
The  S  unites  with  the  tin.     (a.)  Name  the  solid  and  gaseous  pro- 
ducts.    (6.)  How  will  the  volume  of  this  gaseous  product  compare 
with  that  of  the  H2S  decomposed? 

3.  When  &  spiral  of  platinum  wire  is  heated  in  an  atmosphere  of 
H2S,  the  gas  is  decomposed  with  the  deposition  of  solid  S.     What 
volume  of  H  can  thus  be  set  free  from  a  liter  of  H2S  ? 

4.  The  reaction  resulting  from  passing  a  current  of  H2S  through 
an  aqueous  solution  of  Br  is  as  follows  : 

H2S  +  Br2  =2HBr  +  S. 

(a.}  What  volume  of  H2S  is  needed  to  yield  4  I.  of  HBr  ?  (&.)  What 


f*U 


§  142  HYDROGEN   SULPHIDE. 

weight   of  Br  will  thus  combine  with   10  g.   of  H2S?    (c.)  What 
weight  of  Br  will  yield  25  I.  of  HBr  ? 

5.  How  many  grams  of  NH4HO   will  just  neutralize  63  g.   of 
HN03?         /;.-'--  . 

6.  (a.)  How  many  liters  of  0  will  unite  with  20  I.  of  NO  to  form  ' 
N02  ?    (6.)  How  many  each  of  0  and  NO  to  form  30  I.  of  N02  ? 

7.  Arsenic  vapor  is  150  times  as  heavy  as  H.     (a.)  What  is  the 
molecular  weight  of  As  ?    Explain.     (&.)  The  atomic  weight  of  As  is 
75  m.  c.    How  many  atoms  are  there  in  an  As  molecule  ? 

8.  (a.}  What  name  would  you  apply  to  a  substance  that  has  only 
one  kind  of  atoms  ?    (&.)  One  that  has  two  kinds  ?    (c.)  One  that  has 
three  kinds  ? 

9.  Give  Ampere's  Law.    Define  chemistry.  Iv 

10.  Symbolize  the  sulphides  of  Na',  K',  Ag',  Ca",  Cu",  C. 

11.  What  weight  of  S  in  10  I.  of  S  vapor  under  normal  pres- 
sure at  SOOT.  ?    (ft.)  At  1050°C.  ?  ^  , 

12.  Calculate  the  percentage  composition  of  cryolite.    ™(  \ 


4  «r     t<  \     '&  1  13,  0 

^;;/^  •••!}• 

' 


124  SULPHUR     OXIDES    AND    ACIDS.  §  143 


SULPHUR  OXIDES  AND  ACIDS. 

143.  Sulphur  Oxitles.— Sulphur  and  oxygen  unite 
to  form  two  acid-forming  oxides  (or  anhydrides)  symbol- 
ized as  S02  and  S03.     These  unite  with  water  to  form 
the  acids  symbolized  as  H2S03  and  H2S04, 

(a.)  In  addition  to  these,  we  are  acquainted  with  sulphur  sesqui- 
oxide  (S303).  which  has  no  corresponding  known  acid ;  with  hypo- 
sulphurous  acid  (H3S02),  which  has  no  corresponding  known  oxide; 
with  sulphur  peroxide  (S207),  and  with  the  thionic  acids  (§  158). 
The  compound,  S303,  is  called  a  sesquioxide  because  the  number  of 
its  $)  atoms  is  1|  times  the  number  of  its  S  atoms,  the  Latin  prefix, 
sesqui,  meaning  one  and  a  half. 

144.  Sulphur  Dioxide. — This  oxide  of  sulphur 
(sulphurous  oxide,  sulphurous  anhydride,  sulphurous  acid 
gas,  sulphuryl,  S02)  is  the  sole  product  of  the  combustion 
of  sulphur  in  the  air  or  in  oxygen.     It  is  the*only  com- 
pound of  sulphur  and  oxygen  that  can  be  formed  by  direct 
synthesis  (Exps.  36  and  43). 

145.  Preparation. — As  ordinarily  prepared  by  burn- 
ing sulphur  in  the  air,  the  sulphur  dioxide  is  mixed  with 
nitrogen  from  the  air.    When  the  pure  anhydride  is  wanted, 
it  is  generally  prepared  from  strong  sulphuric  acid  by 
heating  it  with  copper,  silver  or  mercury. 

(«.)  Put  20  or  30  g.  of  small  bits  of  copper  and  60  cu.  cm.  of  strong 
H2S04  into  a  flask  and  apply  heat.  The  gas  that  is  evolved  may  be 
purified  by  passing  through  H20  in  the  wash  bottle,  b  (Fig.  67), 
and  then  collected  by  downward  displacement  or  over  mercury  or 
absorbed  in  H.,0,  as  shown  at  c.  A  solution  of  copper  sulphate, 
(blue  vitriol,  CuS04),  remains  in  the  flask. 

2H2S04  +  Cu  =  CuS04  +  2H80  +  S03. 


145 


SULPHUR     OXIDES    AXD    ACIDS. 


125 


(6.)  A  solution  of  S0.z  in  HS0  is  often  wanted  in  the  laboratory. 
It  may  be  formed  by   reducing 
H.,S04  with  charcoal. 
2H2S04  +  C  =  2S08  +2H30  + 
CO,. 

The  mixed  gases  may  be  passed 
through  H20  in  a  series  of 
Woulffe  bottles  (Fig,  34);  very 
little  of  the  C02  will  be  ab- 
sorbed. 

(c.)  It  is  well  to  save  bits  of 
copper,  such  as  pieces  of  wire, 
shells  of  metallic  cartridges,  frag- 
ments of  sheet  copper,  etc.,  for 
they  will  be  of  frequent  US3  in  the 
study  of  chemistry.  pIG 

Experiment  146.— From  the  generating  flask,  a  (Fig.  67),  pass  the 
SO  2  through  a  bottle  or  tube  packed 
in  ice ;  then  dry  the  cool  gas  with 
H2S04  (Exp.  31)*or  CaCI3  (Exp.  28) ; 
then  pass  the  dry  gas  through  a 
U-tube  packed  in  salt  and  pounded 
ice  (Ph.  §  521).  The  S02  will  con- 
dense to  a  liquid  at  the  low  tempera- 
ture thus  produced.  If  the  U-tube 
has  good  glass  stop  cocks,  as  shown 
in  the  figure,  the  liquid  S03  may  bs 
sealed  and  preserved.  Or  the  two 
arms  of  a  common  U-tube  may  have  been  previously  drawn  out  to 
make  a  narrow  neck  upon  each  ;  after  the.  condensation  of  the  S02, 
these  necks  may  be  fused  with  the  blowpipe  flame  and  the  liquid 
thus  sealed  for  preservation. 

Caution. — The  following  experiment  is  hardly  safe  for  performance 
by  the  teacher  in  the  class  or  by  the  pupil.  Such  a  pressure  on  the 
inside  of  a  glass  tube  of  uncertain  qualities,  as  glass  tubes  generally 
are,  is  not  to  be  trifled  with.  Although  less  satisfactory,  it  may  be 
safer  to  rest  the  case  upon  the  assertion  of  the  author. 

Experiment  147. — To  show  the  liquefaction  of  S02  by  pressure, 
draw  out  one  end  of  a  strong  glass  tube  (2  cm.  in  diameter)  to  a  point. 
Fill  the  tube  with  dry  SO  2  by  displacement.  Into  the  open  end,  thrust 
a  snugly  fitting,  greased,  caoutchouc  stopper.  With  a  stout  rod,  force 
the  stopper  into  the  tube  until  the  S02  occupies  about  a  fifth  of  its  orig- 
inal volume.  Liquid  S02  will  collect  at  the  pointed  end  of  the  tube. 


FIG.  68. 


126  SULPHUR     OXIDES    AND    ACIDS.  §  145 

Experiment  148.— Pour  some  of  the  liquid  S08  upon  the  surface 
of  mercury  contained  in  a  capsule,  and  blow  a  current  of  air  over  it 
by  means  of  a  bellows.  The  mercury  will  be  frozen. 

Experiment  149.— If  you  have  a  thick,  platinum  crucible,  heat  it 
red  hot  and  pour  some  of  the  liquid  S02  into  it.  The  S02  will  as- 
sume the  "  spheroidal  state,"  like  that  of  the  globules  of  H2O  some- 
times seen  upon  the  top  of  a  hot  stove,  the  temperature  of  the  liquid 
being  below  its  boiling  point.  If,  now,  a  little  H  2  0  be  poured  in,  the 
SO 2  will  be  instantly  vaporized  by  the  heat  taken  from  the  H20 
(Ph.  §  526),  which  therefore  at  once  becomes  ice.  By  some  dexterity, 
the  lump  of  ice  may  be  thrown  out  of  the  red-hot  crucible. 

Experiment  150.— Wrap  the  bulb  of  an  alcohol  thermometer  in 
cotton  wool  and  pour  some  of  the  liquid  S02  upon  it.  The  change 
of  sensible  into  latent  heat  effected  by  the  vaporization  of  the  SO, 
produces  a  diminution  of  temperature  and  the  thermometer  falls, 
perhaps  as  low  as  — 60° C. 

Experiment  151. — Pour  a  quantity  of  the  liquid  S02  into  nearly 
ice  cold  H20  ;  a  part  will  evaporate  at  once,  another  part  will  dis- 
solve in  the  H20,  and  a  third  part  of  the  heavy,  oily  liquid  will  sink 
to  the  bottom  of  the  vessel.  If  the  part  which  has  thus  subsided 
be  stirred  with  a  glass  rod,  it  will  boil  at  once,  and  the  temperature 
of  the  H20  will  be  so  much  reduced  that  some  of  it  will  be  frozen. 

Experiment  152. — Add  a  few  drops  of  the  aqueous  solution  of  S02 
to  a  weak  solution  of  potassium  permanganate.  The  red  color  will 
disappear,  owing  to  reduction  by  S02. 

Experiment  153. — Burn  some  S  under  a  bell  glass  within  which  are 
some  moist,  bright  colored  flowers.  The  flowers 
will  be  bleached.  The  color  may  be  partly  re- 
stored by  dipping  some  of  the  flowers  into 
dilute  H2S04  and  others  into  NH4HO. 


Experiment  154.  —  Partly  fill  each  of  two 
glasses  with  a  fresh  infusion  of  purple  cabbage. 
Add  a  little  of  the  aqueous  solution  of  S02. 
The  bleaching  action  is  not  very  manifest.  To 
each,  add  cautiously,  drop  by  drop,  a  solution  of 
FIG.  69.  potassium  hydrate  (caustic  potash,  KHO) ;  the 

color  will  disappear.  To  the  contents  of  one  glass,  add  a  little  strong 
H2S04  ;  a  red  color  appears.  To  the  other  add  more  of  the  solution 
of  KHO  ;  a  green  color  appears. 


§  148  SULPHUR    OXIDES    AND    ACIDS.  127 

Experiment  155. — Suspend  a  small  lighted  taper  in  a  lamp  chim- 
ney placed  so  that  a  current  of  air  can  enter  from  below.  At  the 
lower  end  of  the  chimney,  place  a  small  capsule  containing  burn- 
ing  S.  Place  a  piece  of  window  glass  over  the  top  of  the  chimney 
so  as  to  confine  the  S03  within  the  chimney.  The  taper  quickly 
ceases  to  burn. 

146.  Properties. — Sulphur  dioxide  is  a  transparent, 
colorless,  irrespirable,  suffocating  gas.    It  has  a  specific 
gravity  of  32,  being  nearly  2J  times  as  heavy  as  air.    It 
condenses  to   a  liquid   at  — 10°C.,  and  solidifies  when 
cooled  below  — 76°C.     The  liquid  has  a  specific  gravity 
of  1.49,  and  vaporizes  rapidly  in  the  air  at  the  ordinary 
temperature,  producing  great  cold.     It  has  a  great  affinity 
for  oxygen.     Under  the  influence  of   sunlight,  it  unites 
directly  with  chlorine,  acting  as  a  dyad  compound  radical 
and  forming  sulphuryl  chloride,  (S02)"CI2-     It  bleaches 
many  colors,  not  by  destroying  the  coloring  matter,  as 
chlorine  does,  but  by  uniting  with  it  to  form  unstable, 
colorless  compounds.     When,  by  the  action  of  chemical 
agents,  the  sulphur  dioxide  is  set  free  from  the  colorless 
compounds  thus  formed,  the  color  reappears.     It  is  neither 
combustible  nor  a  supporter  of  ordinary  combustion. 

147.  Composition. — The  composition  of  sulphur- 
ous anhydride  is  represented  by  the  following  diagram : 


00  SO2,64w.e. 

32  m.c.\ 

148.  Uses  and  Tests. — Sulphur  dioxide  is  largely 
used  in  the  manufacture  of  sulphuric  acid  and  for  bleach- 
ing straw,  silk  and  woollen  goods.  It  is  also  used  as  an 
antichlor  for  the  purpose  of  removing  the  excess  of  chlo- 
rine present  in  the  bleached  rags  from  which  paper  is 


128  SULPHUR    OXIDES    AND    ACIDS.  §  148 

made,  and  as  an  antiseptic.  When  free,  it  is  easily  detected 
by  its  odor,  familiar  as  that  of  burning  matches,  and  by 
its  blackening  a  paper  wet  with  a  solution  of  mercurous 
nitrate. 

149.  Sulphurous  Acid. — Sulphur  dioxide  is  freely 
soluble  in  water,  forming  sulphurous  acid  (hydrogen  sul- 
phite, H2S03).     When  this  liquid  is  boiled,  it  decomposes 
into  water  and  sulphur  dioxide  ;  when  it  is  cooled  below 
5°C.,  it  yields  a  crystalline  hydrate  of  sulphurous  acid  with 
a  composition  of  H2S03  +  14H20.     On  standing,  it  ab- 
sorbs oxygen  from  the  air  and  changes  to  sulphuric  acid 
(H2S04).     As  one  or  both  of  the  hydrogen  atoms  in  its 
molecule  may  be  replaced  by  a  metal,  it  gives  rise  to  two 
series  of  compounds,  called  sulphites  (§  170).     The  term 
"  sulphurous  acid  "  is  frequently  applied  to  sulphur  diox- 
ide, but  such  use  of  the  term  is  seriously  confusing  and 
objectionable. 

150.  Sulphur  Trioxide.— When  dry  oxygen  and 
dry  sulphurous  anhydride  are  mixed  and  passed    over 
heated  platinum  sponge  or  platinized  asbestos,  they  com- 
bine, forming  dense  fumes  of  sulphur  trioxide  (sulphuric 
oxide,  sulphuric  anhydride,  S03).     When  these  fumes  are 
condensed  in  a  dry,  cool  receiver,  they  form  white,  silky, 
fiber-like  crystals  resembling  asbestos.    Sulphur  trioxide 
may  be  prepared  more  easily  by  gently  heating  Nordhausen 
acid  (§  156)  and  condensing  the  vapor  given  off,  as  in  the 
method  above  described.    When  perfectly  dry,  it  does  not 
exhibit  any  acid  properties  and  may  be  moulded  with  the 
fingers  without  injury  to  the  skin.    It  has  so  great  an  attrac- 
tion for  water  that  it  can  be  preserved  only  in  vessels  her- 


§  152  SULPHUR    OXIDES    AND    ACIDS.  129 

metically  sealed.    It  unites  with  water  with  a  hissing  sound 
and  the  evolution  of  much  heat,  forming  sulphuric  acid. 

S03-fH20  =  H2S04. 

151.  Sulphuric  Acid.— Sulphuric  acid   (hydrogen 
sulphate,  oil  of  vitriol,  H2S04),  occurs  free  in  the  waters 
of  certain  rivers  and  mineral  springs.     It  has  been  esti- 
mated that  one  river,  the  Rio  Viuagre,  in  South  America, 
carries  more  than  38,000  Kg.  of  this  acid  to  the  sea  daily. 
Sulphuric  acid  is  to  the  chemical  arts  what  iron  is  to  the 
mechanical  arts,  as  it  enters,  directly  or  indirectly,  into  the 
preparation   of  nearly  every  substance  with   which  the 
chemist  deals.     It  has  been  said  that  the  commercial  pros- 
perity of  any  country  may  be  well  measured  by  the  quan- 
tity of  sulphuric  acid  that  it  uses. 

152.  Preparation.— Sulphuric  acid  is  formed  by  the 
addition  of  water  to  sulphur  trioxide.     The  water  may  be 
added  at  the  time  of  the  formation  of  the  anhydride  or* 
subsequently.     For  this  purpose,  the  sulphuric  anhydride 
is  formed  by  the  oxidation  of  sulphurous   anhydride  by 
means  of    the    nitrogen    oxides   or  acids.      The  direct 
method  of  oxidation  described  in  §  150  being  too  expen- 
sive, the  indirect  method  soon  to  be  described  is  employed. 

(a.)  In  a  bottle  having  a  capacity  of  1  I.  or  more,  burn  a  bit  of  S. 
In  the  atmosphere  of  S03  thus  formed,  place  a  stick 
(or  a  glass  rod  carrying  a  tuft  of  gun  cotton)  dipped 
in  strong  HN03.  Red  fumes  of  N02  will  appear 
The  red  fumes  show  that  the  HN03  has  been  robbed 
of  part  of  its  0. 

2HN03  +  SO,  =HdS04  +  2N02. 

In  the  presence  of  moisture,  S02  is  able  to  reduco 
(take  0  from)  HN02,  HNO;!,  N.,03  or  N02.  In  the  pro- 
cess just  described,  the  S03  reduced  the  HNO3  ;  the 
HN03  oxidized  the  S02. 


130 


SULPHUR    OXtDES    AND 


152 


(&.)  The  manufacture  of  H2S04  may  be  prettily  represented  by  the 
following  lecture  tabJe  process:  A  large  glass  globe  or  flask  is 
filled  with  air  or  oxygen  and  provided  with  five  tubes,  as  shown  in 
Fi<r.  71.  One  tube  connects  it  with  a  flask  which  furnishes  a  current 
of  S00  (^'8.45,  a.) ;  another  connects  it  with  a  second  fla^  or  bottle, 
which  furnishes  a  current  of  NO  (§  83) ;  the  third  connects  it  with  a 


FIG.  71. 

flask  which  famishes  a  current  of  steam ;  by  the  tube,  d,  a  supply  of 
air  or  0  is  admitted,  from  time  to  time,  into  the  globe.  The  fifth 
tube,  e,  allows  the  escape  of  the  waste  products  of  the  reaction  ;  it 
may  be  connected  with  an  aspirator. 

(1.)  NO  enters  the  globe  and  takes  0  from  the  air.  The  ruddy 
fames  of  N02  are  seen. 

(2.)  On  admitting  a  current  of  S02,  the  red  fames  of  N02  disap- 
pear and  white  "  leaden-chamber  crystals  "  form  on  the  walls  of  the 
globe.  The  N02  has  been  reduced  and  the  S02  oxidized. 

(3.)  On  admitting  steam,  the  crystals  disappear,  and  dilate  H2S04 
collects  at  the  bottom  of  the  globe. 

(4.)  If  air  be  admitted,  red  fumes  again  appear  and  the  process 
may  bo  repeated. 

(e.)  In  the  manufacture  of  HSS04,  the  S02  is  formed  by  burning 
crude  S  or  pyrite  (FeS2)  in  kilns  provided  for  that  purpose.  The 
pyrite,  in  moderately  sized  lumps,  is  placed  on  the  grates  of  the 
kilns,  about  250  Kg.  (500  or  600  lb.}  at  a  time.  When  the  burning 
is  once  started,  it  is  kept  up  by  placing  a  new  charge  on  top  of  the 
one  nearly  burned  out.  The  quantity  of  air  admitted  is  carefully 
regulated  by  a  door  placed  below  the  pyrite  kilns.  The  S02  and 


§152 


SULPHUR     OXIDES    AND    ACIDS. 


131 


other  gases  are  drawn  through  all  of  the  apparatus  by  the  draft  of  a 
large  chimney.  The  nitrogen  oxides  are  furnished,  sometimes  by  a 
continued  supply  of  liquid  HN03  in  the  chambers,  but  more  often  by 
the  reaction  of  sodium  nitrate  and  H3S04  heated  by  the  burning 
pyrite.  The  air,  S02  and  nitrogen  oxides  are  carried  into  a  series  of 
three  or  more  huge  leaden  chambers  where  they  come  into  contact 
with  a  constant  supply  of  steam.  These  lead  chambers  are  some- 
times 30  m,  long,  6  to  7  m.  wide  and  about  5  m.  high,  having  thus  a 
capacity  of  900  to  1000  cu.  m,  or  about  38,000  cu.ft.  They  are  sup- 
ported by  a  wooden  framework,  placed  on  pillars  of  brick  or  iron. 


FIG.  72. 

The  general  appearance  is  shown  in  Fig.  72.  The  H.,S04  formed  in 
the  chambers  accumulates  on  the  floor.  The  process  is  conducted  so 
that  this  "  chamber  acid  "  has  a  specific  gravity  of  1.55,  as  a  stronger 
acid  absorbs  the  nitrogen  oxides.  After  leaving  the  lead  chambers, 
the  nitrogen  oxides,  which  are  supplied  in  excess,  are  absorbed  by 
concentrated  H2S04  in  what  is  called  a  "  Gay-Lussac  tower,"  while 
the  nitrogen  escapes.  The  "chamber  acid,"  which  contains  64  per 
cent,  of  H  2 SO 4,  is  then  concentrated  in  the  "  denitrating  "  or  "  Glover 
tower,"  where  it  is  mixed  with  the  "  nitrated  acid"  from  the  Gay- 
Lussac  tower  and  exposed  to  the  evaporating  influence  of  the  hot 
gases  as  they  pass  from  the  kilns  into  the  chambers,  or  by  evapora- 
tion in  leaden  pans,  until  it  has  a  specific  gravity  of  1.7  and  contains 
7Sper  cent,  of  H2SO4.  If  concentrated  beyond  this  point,  the  hot 


132  SULPHUR     OXIDES    AND    ACIDS.  §  152 

acid  attacks  the  lead  of  the  pans.  In  this  form,  the  acid  is  techni- 
cally called  brown  oil  of  vitriol  as  it  is  slightly  colored  by  organic 
impurities.  It  is  largely  sold  for  a  great  variety  of  purposes. 
Further  concentration  and  purification  are  carried  on  in  glass  retorts 
of  from  75  to  150  £.  capacity  or  in  large  platinum  stills  (some of  which 
cost  as  much  as  £6,000).  until  the  liquid  contains  98  per  cent,  of 
H.>S04  and  has  a  specific  gravity  of  upwards  of  1.8. 

(d)  Although  we  have  no  reason  to  think  that  some  of  the  reac- 
tions in  the  manufacture  of  H2S04  are  not  simultaneous,  we  may, 
with  propriety,  trace  them  as  if  they  were  really  consecutive  ;  e.  g., 

(i:>  S  +  03  =  S02. 

(2.)  2HN03  +  S03  =  H2S04  +  2N02. 

(3.)  S03  +  N02  =  S03  +  NO. 

(4.)  S03  +  H20  =  H2S04. 

(5.)  NO  +  0  =  N02. 

In  reality,  most  of  the  0  used  for  the  oxidation  of  the  S02  comes 
from  the  air,  admitted  to  the  chambers  through  the  kiln.  The  part 
taken  in  the  process  by  the  nitrogen  %xide  is  very  interesting,  it  act- 
ing as  a  carrier  of  O  from  the  air  to  the  S0'8.  Theoretically,  but  not 
practically,  a  single  molecule  of  HN03  or  of  NO  would  be  sufficient 
for  the  manufacture  of  an  unlimited  amount  of  H2S04,  as  maybe 
seen  by  repeating  the  equations  above  (omitting  the  second)  in  a 
series  continued  to  any  extent  desired.  But,  since  air  is  used  instead 
of  pure  O,  the  N  thus  introduced  into  the  chambers  has  to  be  re- 
moved, and,  in  its  passage  out,  sweeps  away  much  of  the  nitrogen 
oxides,  which  then  have  to  be  supplied  anew. 

Experiment  156. — Place  27  cu.  cm.  of  H2O  in  a  graduated  tube. 
Slowly  add  73  cu.  cm.  of  H2S04.  When  the  mixture  has  cooled, 
notice  that  its  volume  is  about  92  cu.  cm.  instead  of  100  cu.  cm. 

Caution. — In  mixing  H20  and  H2S04,  pour  the  H2S04  into  the 
H20,  not,  the  H20  into  the  H2S04.  If  the  lighter  liquid  be  poured 
on  top  of  the  heavier,  it  will  float  there  and  great  heat  will  be  de- 
veloped at  the  level  where  they  come  into  contact.  This  heat  might 
form  steam  of  sufficient  tension  to  burst  through  the  heavier  liquid 
above  and  do  damage  by  scattering  the  H2S04.  When  the  above 
directions  are  followed,  the  H2S04  mixes  with  the  H20  as  it  falls 
through  it. 

Experiment  157. — Place  30  cu.cm.  of  H30  in  a  beaker  glass  of 
about  250  cu.  cm.  capacity.  Into  this,  pour  70  cu.  cm.  of  concentrated 
H2S04  in  a  fine  stream.  Stir  the  mixture  with  a  test  tube  contain- 


§  153  SULPHUR    OXIDES    AND    ACIDS.  133 

ing  alcohol  or  ether,  colored  with  cochineal  or  other  coloring  matter. 
The  liquid  in  the  test  tube  will  boil.  Holding  the  test  tube  in  a  pair 
of  nippers,  ignite  the  vapor  escaping  from  the  test  tube.  The  test 
tube  may  be  closed  with  a  cork  carrying  a  delivery  tube  and  the  jet 
ignited.  It  will  give  a  voluminous  flame.  With  a  chemical  ther- 
mometer (App.  3),  take  the  temperature  of  the  liquids  before  and 
after  mixture.  If  the  test  tube  stirrer  contain  H2O  instead  of  the 
more  volatile  liquids  mentioned,  the  H20  will  boil. 

Expzriment  158. — Dip  a  splinter  of  wood  into  H2S04.  It  will  be 
charred  as  if  by  fire. 

Experiment  159. — Dissolve  50  g.  of  crystallized  sugar  in  20  cu.  cm. 
of  hot  H20.  To  this  syrup,  when  cool,  add  a  little  H2S04  and 
stir  the  two  together.  The  mixture  will  become  hot  and  form  'a 
voluminous,  black  porous  mass. 

;  153.  Properties. — The  sulphuric  acid  of  commerce 
is  largely  known  as  oil  of  vitriol.  It  has  a  specific  gravity 
of  about  1.82.  It  generally  contains,  as  impurities,  lead 
sulphate  from  the  chambers  and  evaporating  pans,  and 
arsenic  from  the  pyrite.  For  most  purposes,  however,  it 
answers  as  well  as  the  "  H2S04,  C.P.,"  or  chemically  pure 
acid.  The  pure  acid  is  a  colorless,  oily,  very  corrosive 
liquid  with  a  specific  gravity  of  1.842  at  the  ordinary 
temperature  (1.854  at  0°C.  and  1.834  at  24°C.).  It  has  a 
very  remarkable  attraction  for  water,  the  combination 
being  marked  by  a  condensation  of  volume  and  the  evolu- 
tion of  much  heat.  It  may  be  mixed  with  water  in  all 
proportions.  When  exposed  to  the  air  at  ordinary  tem- 
peratures, it  does  not  vaporize  but  absorbs  water  from 
the  atmosphere,  thus  increasing  both  its  weight  and  vol- 
ume. On  account  of  this  hygroscopic  action,  it  should  be 
kept  in  well  stoppered  bottles. 

Sulphuric  acid  removes  water  from  many  organic  sub- 
stances, completely  charring  some,  like  sugar  and  woody 
fiber,  and  breaking  others,  as  alcohol  and  oxalic  acid,  into 


134  SULPHUR     OXIDES    AND    ACIDS.  §  153 

new  compounds  (see  §§  213  and  193).  It  is  one  of  the 
most  energetic  acids  known.  Diluted  with  1,000  times  its 
bulk  of  water,  it  still  reddens  blue  litmus.  It  liberates 
most  of  the  other  acids  from  their  salts. 

154.  Uses. — Sulphuric  acid  is  used  as  a  drying  agent 
for  gases,  in  the  preparation  of  most  of  the  other  acids,  in 
the  manufacture  of  soda,  phosphorus  and  alum,  in  the 
preparation  of  artificial  fertilizers,  in  the  refining  of  pe- 
troleum, in  the  processes  of  bleaching,  dyeing,  etc.    In 
fact,  there  is  scarcely  an  art  or  trade  in  which,  in  some 
form  or  other,  it  is  not  used,  it  being  employed  directly  or 
indirectly  in  nearly  all  important  chemical  processes.     It 
is  the  most  important  chemical  reagent  we  have  and  is 
made  in  immense   quantities,  upwards  of   850,000  tons 
being  produced  yearly  in  Great  Britain  alone. 

155.  Tests. — The  most  convenient  test  for  free  sul- 
phuric acid  is  the  charring  of  organic  substances.    A  paper 
moistened  with  a  natural  water  containing  the  free  acid, 
and  then  dried  at  100°C.  will  be  completely  charred.    The 
acid  or  solutions  of  its  salts  give  a  white  insoluble  precip- 
itate with  barium  chloride  or  calcium  chloride. 

156.  Nordhauseii  Acid.— Nordhausen  acid  (disul- 
phuric  acid,  fuming  sulphuric  acid,  H2S207),  is  prepared 
by  the  distillation  of  dried  iron   sulphate   (green  vitriol, 
FeS04),  in  earthen  retorts.    It  is  a  heavy,  oily  liquid  with 
a  specific  gravity  of  1.89.     It  fumes  strongly  in  the  air 
and  hisses  like  a  hot  iron  when  dropped  into  water.    It  is 
used  chiefly  for  dissolving  indigo. 

(#.)  The  name,  Nordhausen  acid,  is  due  to  the  fact  that  it  was 
formerly  prepared  in  Nordhausen,  Saxony.  At  the  present  time,  the 
acid  comes  almost  wholly  from  Bohemia.  The  propriety  of  the 


§  159  SULPHUR     OXIDES    AND    ACIDS.  135 

term,  disulplmric  acid,  is  shown  by  tLe  equation,  2H2S04  —  H2O  = 
H3S.,07.  It  may  be  considered  as  S0a  dissolved  in  H.,S04,  for,  when 
heated,  it  separates  into  those  substances,  H^SjjOy  =  S03  +  H.,S04. 

157.  Sulphur  Scsquioxicle  and    Hyposiilphuroiis 

Aciclx.  —  Sulphur  sesquioxide  (S203)  is  a  rare,  bluish  green  com- 
pound, resembling  malachite  in  appearance.  It  easily  decomposes 
into  sulphur  dioxide  and  sulphur.  Hyposulphurous  acid  (H2S02)  is 
a  very  unstable,  yellow  liquid  with  powerful  reducing  properties. 
Its  salt,  hydrogen  sodium  hyposulphite  (HNaS03),  is  used  for  the  re- 
duction of  indigo  in  dyeing  and  calico  printing. 

158.  Thioilic  Acids.  —  Besides  the  foregoing,  there 
is  a  well  defined  series  of  sulphur  acids,  but  they  are  of 
much  less  importance.    Their  corresponding  oxides  are 
unknown. 

(a.)  Thiosulphuric  acid  .................   .  .  .  H2S203 

Dithionic  acid  ..........................  H2S206 

Trithionic  acid  ..........................  HgSgOg 

Tetrathionic  acid  ........................  H  2S406 

Pentathionic  acid  ...................  ....  ,H2S50C. 

(&.)  The  thiosulphuric  acid  is  better  known  by  the  misnomer  of 
"hyposulphurous  "  acid,  which  properly  designates  the  compound 
symbolized  by  H2SO».  In  similar  manner,  the  thiosulphates  (e.  g., 
sodium  thiosulphate,  Na2S203),  are  commonly,  but  improperly, 
spoken  of  as  "  hyposulphites." 

Note.  —  The  word,  thionic,  comes  from  the  Greek  name  for  S. 

159.  Sulphur  Oxide§  and  Oxyaci«l§.—  The  known  sul- 
phur oxides  and  oxyacids  are  symbolized  in  tabular  form  below  for 
purposes  of  convenient  study  : 


OxHesj  ......  [Sa03 


SO, 


SO, 


Acids.  |H2S03   ....    HaSO,  HaS01!HsSa03H3SzOaH4S3OaH2S1OeH2SsO, 


u 

136  SULPHUR     OXIDES    AND    ACIDS.  §  159 


- 
6fV         EXERC 


jXERCISES. 

1.  (a.)  What  is  the  molecular  weight  of  S02?    (&.)  The  specific 
gravity  of  the  gas  ?    (c.)  Its  percentage  composition  ? 

2.  H2Sand  S03  are  often  found  in  volcanic  gases.     When  they 
vt>'V    come  into  contact,  they  decompose  each*  other.     Write  an  equation 
J0-JiJjl  explaining  the  occurrence  of  native  S  in  volcanic  regions.  H-^«  f-Wv£,*"'< 

3.  Why  can  not  H2S04  be  used  for  drying  H,S  (Exp.  141 ). 

4.  (a.)  How  much  HN03  can  be  formed  from  306  g.  of  KN08?" 
(&.)  Haw  much  H2S04  will  be  required  ?    (c.)  What  will  be  the  yield 
of  HNaS04  ?    (d.)  If  the  product  be  Na3S04,  what  will  be  the  amount 
thereof? 

5.  Write  the  graphic  symbol  for  H2S04  :  (a,)  Representing  S  as  a 
dyad.     (&.)  As  a  hexad.  tf  ~  f ^ ' '  S  \  ^'^ '  //    /  H^  0  -  £  -  h 

6.  Write  the  graphic  symbol  for  H2S207,  introducing  S03  twice 
as  a  bivalent  radical.    (H2S207  =  auhydrosulphuric  acid.)#-0-  ^v-** 

7.  The  symbol  for  potassium  sulphate  is  K2S04 ;  that  for  lead  sul- 
phate is  PbS04.     (a.)    What  is  the  quantivalence  of  potassium? 
(&.)  Of  lead?    (See  §60.) 

8.  How  would  you  write  the.  symbol  of  a  binary  compound  con- 
taining a  dyad  and  a  triad  ? 

9.  How  much  JHNO^  will  just  neutralize  1200 ,#.  of  ammonium 
hydrate ?      * 0t  ft  vT »','  ?f  ,'  ^f  *£  ^ . 

10.  (a.)  How  much  NH3  may  be  formed  from  42.8  g.  of  NH4CI  ? 
(&.)  How  much  CaH202  must  be  used? 

11.  (a.)  What  volume  of  Cl  may  be  obtained  from  1  /.  of  dry  HCI  ?  -£ 
(&.)  What  weight?  -£/  3U  /  f  -  /fj       ff* 

13.  When  aeriform   H20  and  Cl  are  passed  through  a  porcelain 
tube  heated  to  redness,  HCI  and  0  are  formed,     (a.)  Write  the  reac- 
tion in  molecular  symbols.     (&.)  What  volume  of  O  may  be  thus 
obtained  from  2  1.  of  steam?    (c.)  How  will  the  volume  of  HCI     * 
formed  compare  with  that  of  the  0  ?    (d.)  In  what  simple  way  may   • 
the  0  be  freed  from  mixture  with  HCI  ?' 

13.  (a.)  From  100  g.  of  KCI03,  how  many  grams  of  0  may  be  ob- 
tained?   (6.)  How  many  liters? 

14.  H20  and  N  are  among  the  products  formed  when  NH^CI  and        .  -, 
NaN02  are  heated  together  in  a  flask.     Write  the  reaction.  "''" '- 

15.  (ft.)  I  mix    H   and  Cl,  and  expose  the  mixture  to  sunlight/' K  C* 
What  happens?     (&.)  I  add  NH3  to  the  product  just  formed.     What 

is  the  name  of  this  second  product  ? 

16.  What  is  the  more  common  name  for  oxygen  dioxide  ? 


^  #*J* 


§  l6l  SELENIUM    AND    TELLURIUM.  137 


SELEN'IUM    AND    TELLURIUM. 

SELENIUM  ;  Symbol,  Se ;  specific  gravity,  4.3  to  4.8  ;   atomic 
weight,  79  m.  c.  ;  molecular  weight,  158  in.  c. 

16O.  Selenium. — This  element  is  a  rare  substance, 
of  little  industrial  importance,  but  of  considerable  interest 
to  the  chemist.  It  is  occasionally  found  free,  but  generally 
in  combination  as  a  selenide.  Like^ sulphur,  it  exists  in 
several  allotropic  forms.  The  native  form  melts  at  about 
217°C.  and  boils  with  a  deep  yellow  vapor  below  a  red  beat. 
In  its  leading  properties  and  chemical  behavior,  it  re- 
sembles sulphur,  as  will  appear  in  §  162.  It  burns. with 
an  odor  resembling  that  of  decaying  cabbages.  It  offers  a 
very  great  resistance  to  the  passage  of  the  electric  current, 
the  resistance  being  wonderfully  diminished  by  the  action 
of  light.  The  property  last  mentioned,,  has  recently  been 
utilized  in  the  construction  of  the  ph otophone  and  the 
element  thus  endowed  with  added  interest  and  impor- 
tance. 


TELLURIUM  ;  Symbol,  Te  ;  specific  gravity,  6.25  ;  atomic  weight, 
128  m.  c. ;  molecular  weight,  256  m.  c. 

161.  Tell urium.— This  element  is  even  more  rare 
than  selenium.  It  has  a  metallic  lustre  and  in  some  of  its 
physical  properties,  such  as  the  conduction  of  heat  and 
electricity,  it  resembles  the  metals.  It  melts  at  about 
500°C.  and  volatilizes  at  a  white  heat  in  a  current  of  hy- 
drogen. Its  chemical  bel^7ior,  however,  allies  it  to  sul- 
phur and  selenium.  With  hydrogen,  it  forms  hydrogen 


138 


THE    SULPHUR    GROUP. 


§i6i 


telluride  (H2Te),  which  can  not  be  distinguished  by  its 
smell  from  hydrogen  sulphide. 

Note. — The  name,  xeleidum,  is  from  the  Greek  word  meaning  the 
moon,  and  the  name,  tellurium,  from  the  Greek  word  meaning  the 
earth. 

162.  The  Sulphur  Group.  —  Oxygen,  sulphur, 
selenium  and  tellurium  form  a  natural  group.  The  resem- 
blances between  the  last  three  members  of  the  group  are 
as  well  marked  as  those  of  the  chlorine  group.  As  the 
atomic  weight  increases,  the  chemical  activity  diminishes, 
selenium  being  about  midway  between  sulphur  and  tellu- 
rium. Their  specific  gravities,  melting  and  boiling  points, 
show  a  similar  gradation. 

(a.)  Some  of  the  chemical  resemblances  of  the  members  of  this 
group  are  easily  visible  in  the  following  table : 


Hydrogen 
oxide. 
H30 

Hydrogen 
sulphide. 
H2S 

Hydrogen 
selenide. 
H2Se 

Hydrogen 
telluride. 
H2Te 

Iron  oxide. 
FeO 

Iron  sulphide. 
FeS 

Iron  selenide. 
FeSe 

Iron  tetturide. 
FeTe 

•  •  •  • 

Sulphur 
dioxide. 
S02 

Selenium 
dioxide. 
Se02 

Tellurium 
dioxide. 
Te02 

.... 

Sulphur 
trioxide. 
S03 

Selenium 
trioxide. 
Se03  (?) 

Tellurium 
trioxide. 
Te03 

.... 

Sulphurous 
acid. 
H2S03 

Selenous 
acid. 
H2Se03 

Tellurous 
acid. 
H2Te03 

Sulphuric 
acid. 
H2S04 

Selenic 
acid. 
H2Se04 

Telluric 
acid. 
H2Te04 

Ethyl  oride 
(ethert. 
(C2H5)20 

Ethyl 
sulphide. 
(C8H5)2S 

Ethyl 
selenide. 
(C2H5)2Sa 

Ethyl 
telluride. 
(C2H5)2Te 

Ethyl  hydrate 
(alcohol}. 
(C2H5)HO 

Ethyl  hydrogen 
sulphide. 
(C2H5)HS 

Ethyl  hydrogen 
selenide. 
(C2H5)HSe 

Ethyl  hydrogen 
telluride. 
(C2H5)HTe 

§  l62 


THE 


1.  (a.)  Give  the  physical  and  'chemical  properties  of  H.    (6.)  Ex- 
plain the  structure  of  an  oxy-hydrogen  blowpipe. 

2.  What  chemical  process  is  illustrated  when  you  prepare  H  ? 

3.  («.)  State  two  ways  in  which  the  analysis  of    H20   may  be 
effected.     (&.)  Give  the  composition  of  HaO  by  volume  and  by  weight. 
(c.)  What  weight  of  each  constituent  in  a  Kg.  of  H20  ? 

/#,'/  4.  A  chemist  wishes  50  Kg.  of  H.     What  substances  shall  he  use 
^5"  in  making  it,  and  how  much  of  each  ?/  fa  JL  f  '  jf}*f 

5.  (0.)  H2S04  is  poured  upon  nitre  ;  name  the  two  substances  that 
you  obtain,    (b.)  Write  the  reaction,  hf  v^^i  «W#j  -WS^  +  ft  / 
.j.        6.  (a.)  What  is  the  least  amount  of  HgS04  that  will  completely  /^4  < 
'.'/react  with  4  Ib.  of  KNO8?    (6.)  How  much  will  the  liquid  product      -/' 
''  r  weigh  I  .    '&&C    fi*QL"V-  ^^  ^ 

7.  («.)  From  8  ^  ofTCNOi,  how  much  HN03  can  be  liberated  fl^*?/ 


How  much  H2S04  is  the  least  that  would  be  required? 
(a.)  Give  the  names  and  symbols  for  the  oxides  of  N.     (6.)  Give 
the  law  of  multiple  proportion. 

9.  (a.)  What  is  the  difference  between  air  and  water,  chemically 
considered?    (&.)  Give  one  chemical  and  one  physical  property  of  0 
and  of  NH3. 

10.  Write  the  reactions  for  the  preparation  of  Cl,  HF,  S02,  H2S, 
and  state  at  least  one  leading  property  of  each. 

11.  When  a  hot  metallic  wire  is  plunged  into  a  certain  binary  acid 
gas,  violet  fumes  are  seen.     What  is  the  gas?  H  j 

12.  (a.)  How  is  Cl  obtained?    (&)  Explain  the  reaction,     (c.)  Give 
the  most  remarkable  chemical  properties  of  the  substance. 

13.  (a.}  What  is  the  most  common  compound  of   Cl  ?    (b.)  Find 
its  percentage  composition.     ^.  7$'' 

14.  (a.)  Give  the  atomic  weight  of  each  of  the  elements  that  you 
have  studied.    (&.)  What  is  meant  by  atomic  weight  ? 


ACIDS,  BASES,  SALTS,  ETC. 

163.  Acids.— -The  word  acid  is  difficult  of  satisfactory 
definition.  The  term  signifies  a  class  of  compounds  that 
generally  have  a  sour  taste,  a  peculiar  action  upon  vegeta- 
ble colors  (e.  g.,  the  reddening  of  blue  litmus),  and  that 
unite  with  other  compounds  (bases)  of  an  opposite  quality 
to  form  a  third  class  of  compounds  (salts)  possessing  the 
characteristics  of  neither  of  the  first  two  classes.  Tlie 
only  constituent  common  to  all  acids  is  hydrogen 
which  is  replaceable  with  an  electro-positive  or 
metallic  element. 

(a.)  The  term,  acid,  is  sometimes  used  to  designate  certain  com- 
pounds that  contain  no  H,  as  S02,  C02,  etc.  Such  use  of  the  term  is 
incorrect  and  seriously  confusing. 

(&.)  The  binary  acids  consist,  almost  exclusively,  of  H  Combined 
with  some  member  of  the  halogen  group  (§123).  Their  names  all 
have  the  termination  -ic. 

(c.)  We  may  suppose  the  ternary  acids  to  be  formed  of  hydroxyl 
(HO,  §  44),  and  a  negative  radical,  as  : 

.0 


HNO, 


H2S04 


(HOHN02) ;        H-0-(N02) ;  H-0-f/ 


(HO)3=(S03);  H-0-(S02)-0-H 


H3P04;  (HO)3E(PO);   H-0-(PO)-0-H  ; 

Phosphoric  acid. 


0 

II 

H-0-S-O-H. 
II 
0 

o 

II 

H-0-P-O-H. 


The  atom  of  "  saturating  "  0  shown  in  each  case  in  the  fourth 
column  becomes  a  part  of  the  negative  radical  as  shown  in  the  second 


§  1  64  ACIDS,    BASES,    SALTS,  ETC.  141 

and  third  columns.  Similarly,  the  '-linking  "  oxygen  becomes  a  part 
of  the  hydroxyl. 

((Z.)  Acids  take  their  names  from  their  non-metallic  or  negative 
radicals.  If  only  two  ternary  acids  of  a  non-metallic  element  are 
known,  the  one  in  which  the  molecule  contains  the  greater  number 
of  O  atoms  takes  the  termination  -ic  ;  the  other  takes  the  termina- 
tion -ous.  Sometimes  the  radical  forms  three  or  even  four  ternary 
acids.  The  acid  in  which  the  molecule  contains  a  number  of  0 
atoms  greater  than  that  of  the  -ic  acid  takes  the  prefix  per-  ;  the  one 
in  which  the  number  is  less  than  that  of  the  -ous  acid  takes  the 
prefix,  hypo-.  The  use  of  these  prefixes  and  suffixes  will  be  made 
clear  by  a  study  of  the  following  examples  : 

HCI04  ......  .perchloric  acid.  I 

HCI03  ..........  chlone  acid.  I  H2S04  ........  sulphun'c  acid. 

HCI03     .......  chlor0ws  acid.      H2S03  ......  sulphmws  acid. 

HCIO    ....  hypoch\owus  acid.  |  H2S02  .  .hyposvdphuwus  acid. 

Unfortunately,  there  is  a  lack  of  uniformity  among  chemists  in 
the  nomenclature  of  acids  and  salts  ;  hence,  a  certain  amount  of  con- 
fusion in  the  literature  of  the  science.  (See  §  60.) 

164.  Basicity  of  Acids.  —  The  hydrogen  of  an, 
acid  that  may  be  replaced  by  a  metal  is  called  basic  hydro- 
gen. If  the  acid  molecule  has  one  atom  of  basic  hydro- 
gen, the  acid  is  called  a  mono-basic  acid.  If  it  has  two 
such  atoms,  the  acid  is  called  a  di-basic  acid.  Similarly, 
we  have  tri-basic  and  tetra-basic  acids. 

(«  .)  The  basicity  of  an  acid  molecule  depends  upon  the  number  of 
its  directly  exchangeable  H  atoms  and  may  generally  be  represented 
by  the  number  of  hydroxyl  groups  it  contains.    For  example  : 
HN03  is  a  mono-basic  acid  ..................  (HO)  —  (N08)'. 


H2S04  is  a  di-basic  acid  ....... 

(HO) 
H3P04  is  a  tri-basic  acid  ....................  (HO)  —  (PO)'". 


Be  it  remembered,  however,  that  the  basicity  of  an  acid  molecule 
depends,  not  upon  the  total  number  of  its  H  atoms,  but  upon  the 
number  of  them  that  are  endowed  with  this  peculiar  power  of  direct 
exchange  from  metallic  atoms.  H3P04  is  called  tribasic,  not  be- 
cause it  has  three  H  atoms  but  because  it  may  form  three  distinct 
salts  with  one  metal  (§  170). 


142  ACIDS,    BASES,    SALTS,    ETC.  §  165 

.165.  Anhydrides.— An  oxide  of  a  non-metallic  (or 
electro-negative)  element,  which,  with  the  elements  of 
water,  forms  an  acid,  is  called  an  anhydride.  Nitrogen 
peroxide  (N205)  and  sulphunc  and  sulphurous  oxides  are 
anhydrides.  Acid  oxide  is  a  better  name. 

166.  Bases. — The  word  base  indicates  a  very  impor- 
tant class  of  ternary  compounds,  opposed   in  chemical 
properties  to  the  acids.    The  bases  restore  most  colors  that 
have  been  reddened  by  an  acid.     Like  the  acids,  they  may 
be  considered  hydroxyl  compounds ;  unlike  the  acids,  their 
hydroxyl  is  united  with  a  metallic  (or  electro-positive) 
radical.     The  chief  characteristic  of  a  base  is  its  power  of 
reacting  with  an  acid  to  form  water  and  a  salt.      The 
characteristic  difference  between  an  acid  and  a  base  is  that 
the  hydrogen  of  the  former  may  be  replaced  by  a  metallic 
atom ;  that  of  the  latter  by  a  non-metallic  atom. 

(a.)  The  term,  base,  is  frequently,  but  ill-advisedly,  used  to  desig- 
nate certain  compounds  that  neutralize  acids  and  form  salts  but  that 
contain  no  H,  as  CaO  (§  290),  etc.  Basic  oxide  is  a  better  name. 

(6.)  The  H  of  a  base  that  may  be  replaced  by  a  non-metallic  ele- 
ment is  called  acid  hydrogen.  We  have  mon-acid,  di-acid,  tri-acid 
bases,  etc.  KHO,  Ca(HO)2,  AI(HO)3  and  Ti(HO)4  represent  bases. 

(c.)  "The  hydroxyl  compounds  of  the  elements  that  have  a 
markedly  metallic  character  are  bases.  The  hydroxyl  compounds  of 
the  elements  that  have  a  markedly  non-metallic  character  are  acids. 
The  hydroxyl  compounds  of  the  elements  that  are  neither  mark- 
edly metallic  nor  non-metallic  sometimes  act  as  bases  and  some- 
times as  acids.  Thus,  SbO(HO),  antimonyl  hydroxide,  is  a  weak 
base  or  a  weak  acid,  exhibiting  one  character  or  the  other  according 
to  the  nature  of  the  compound  with  which  it  is  brought  into  con- 
tact." 

167.  Hydrates. — The  basic  oxides  unite  with  water 
to  form  hydrates  or  hydroxides.      Thus,  K20  -f  H20  — 
2KHO,  potassium  hydrate  or  caustic  potash.    In  similar 


§  l6p  ACIDS,    BASES,     SALTS,    ETC.  143 

manner,  we  may  produce  Na'HO,  sodium  hydrate ;  Ca"(HO)2 
or  Ca"H202,  calcium  hydrate,  etc.  The  hydrates  are 
bases. 

(a.)  A  hydrate  may  be  considered  as  a  metallic  compound  of 
hydroxyl. 

(&.)  Some  of  tlie  hydrates  yield  solutions  that  corrode  the  skin  and 
convert  the  fats  into  soaps.  They  are  called  alkalies.  Potassium 
and  sodium  hydrates  are  alkalies. 

168.  Basic  Ammonia.  —  Ammonia  water,  in  its 
physical  relations,  resembles  a  simple  aqueous  solution  of 
a  gas,  while,  in  its  chemical  relations,  it  acts  like  an  alka- 
line hydrate.  On  this  account,  its  symbol  is  often  written 
on  the  water  ty^oe,  thus :  (NH*)'  I  0,  or  (NH4)HO.  This 

symbol  assumes  the  existence  of  a  univalent  compound 
radical,  NH4.  This  purely  hypothetical  radical  is  called 
ammonium,  and  is  considered  a  metal.  The  grottpiJNxf 
frequent  occurrence  in  combination.  Ammonium  hydrate, 
(NH4HO)  has  been  termed  « the^ volatile  alkali." 

Experiment  160. — Repeat  Effj.  78.  The  ammonium  nitrate  thus 
produced  is  the  substance  we  used  in  the  preparation  of  nitrous 
oxide  (N20). 

HN03  +  (NH4)HO  =  (NH4)N03  +  H20. 

Experiment  161.  —  Repeat  Exp.  160  using  a  dilute  solution  of 
potassium  hydrate  (caustic  potash,  KHO)  instead  of  NH4HO.  The 
crystals  thus  produced  are  KN03,  the  substance  used  in  preparing 
HN03(§74,  a). 

A  HN03  +  KHO  =  KN03  +  H20. 

'169.  Salts. — In  the  experiments  just  given,  the  pro- 
ducts of  the  metathesis  were  water  and  a  new  class  of  com- 
pounds called  salts,  so  named  on  account  of  their  general 
resemblance  to  common  salt  (NaCI),  a  type  of  this  class  of 
compounds.  A  salt  is  a  compound  formed — 

(1.)  By  replacing  one  or  more  of  the  hydrogen  atoms  of  an  acid 
with  electro- positive  (metallic)  atoms  or  radicals.  Compare  HN03 
and  KN03. 


144  ACIDS,    BASES,    SALTS,    ETC. 

(2.)  By  replacing  one  or  more  of  the  hydrogen  atoms  of  a  base  with 
electro-negative  (non-metallic)  atoms  or  compound  radicals.  Compare 
KHO  and  K(N02)0  or  KN03. 

(3.)  By  the  direct  union  of  an  anhydride  and  a  basic  oxide.  Thus, 
calcium  sulphate  results  from  the  direct  union  Of  sulphuric  anhy- 
dride and  calcium  oxide  (quicklime):  S03  +  CaO  =  CaS04. 

Note.—Qi  these  three  views  of  the  formation  of  a  salt,  the  first  is 
the  one  most  frequently  taken,  but  occasionally  the  other  two  are 
convenient.  An  acid  is  sometimes  called  a  "  hydrogen  salt ;"  e.  g., 
hydrogen  nitrate  (HN03). 

17O.  Classification  of  Salts.— -Salts  may  be  nor- 
mal (or  neutral),  double,  acid  or  basic. 

(a.)  A  normal  salt  is  one  that  contains  neither  basic  nor  acid  H. 
All  of  the  basic  H  of  the  acid  or  acid  H  of  the  base  from  which  it 
was  formed  has  been  replaced  as  stated  in  the  last  paragraph. 
K2S04  and  CuSO^  are  normal  salts. 

(&.)  A  double  salt  is  one  in  which  H  of  the  acid  from  which  it  was 
formed  has  been  replaced  by  metallic  (or  positive)  atoms  of  dif- 
ferent kinds.  Forexample,  common  alum,  AI2'"K2'(S04)4,  is  a  double 
salt. 

(c.)  An  acid  or  hydrogen  salt  is  one  that  contains  basic  H.  Only 
part  of  the  H  of  the  acid  from  which  it  was  formed  has  been  re- 
placed, on  account  of  which,  in  most  cases,  it  still  acts  like  an  acid, 
reddening  blue  litmus.  The  hydrogen  potassium  sulphate,  HKS04, 
mentioned  in  §  74  (a.)  is  an  acid  or  hydrogen  salt. 

(d.)  A  basic  salt  is  one  that  contains  acid  H.  Only  part  of  the  H 
of  the  base  from  which  it  was  formed  has  been  replaced,  on  account 
of  which,  in  many  cases,  it  still  acts  like  a  base,  turning  reddened 
litmus  to  blue.  For  example,  lead  hydrate  is  a  base  with  the  sym- 
bol, Pb"H2O2  or  H2Pb02.  Replacing  half  of  this  H  with  the  acid 
radical,  N02,  we  have  H(N02)PbOo,  the  symbol  for  lead  hydro- 
nitrate,  a  basic  salt. 

(e.)  A  binary  acid  will  yield  a  binary  salt  when  its  H  is  replaced. 
Thus,  HCI  yields  NaCI. 

171.  Siilplnir  Salts. — In  the  ternary  compounds  (acids,  bases, 
and  salts)  so  far  studied,  the  molecules  have  been  bound  or  linked 
together  by  bivalent  oxygen.  But  there  is  another  distinct  class  of 
ternary  molecules  in  which  the  constituent  atoms  are  linked  together 


§  171  ACIDS,    BASES,    SALTS,    ETC.  145 

by  bivalent  sulphur.  In  these  molecules,  the  sulphur  may  be 
"  linking,"  "saturating,"  or  both.  The  compounds  are  named  and 
symbolized  in  the  same  way  as  the  corresponding*  oxygen  compounds. 
Thus  : 

The  type  H  —  0  —  H  has  its  analogue  in  H  —  S  —  H  or  H2S. 

KHOorK  —  0  —  H  "  "         K  —  S  —  H. 

KoC03orK,  =  02  =  (CO)"  "         K3  =  S2  =  (CS)or  K2CS3. 

In  nomenclature,  these  "sulphur  salts,"  (in  which  term,  acids  and 
bases  are  included)  are  distinguished  from  the  corresponding  "  oxy- 
gen salts"  by  prefixing  sulpha-.  Thus,  the  analogue  of  potassium 
hydrate  is  called  potassium  sulphohydrate  ;  that  of  potassium  car- 
bonate is  called  potassium  sulphocarbonate.  The  "sulphur  salts" 
are  not  so  numerous  or  so  well  know*  as  the  "  oxygen  salts," 


EXEECISES. 

1.  (a.)  What  is  the  difference  between  an  atom  and  a  molecule  ? 
(b.)  Between  a  physical  and  a  chemical  property?    (cf)  Define  and 
illustrate  base,  acid,  salt.  -  (d.)  State  the  differences  between  an  -jc, 
an  -ous,  and  an  -ate  compound. 

2.  (a.)  Why  is  sulphurous  acid  said  to  be  dibasic?    (&.)  What  is 
the  difference  between  an  acid  sulphite  and  a  normal  sulphite  ?    (c.) 
Between  an  acid  sulphite  and  a  hydrogen  sulphite  ? 

3.  (a.)  Write  the  empirical  symbol  for  the  hydrate  of  the  monad 
radical,  nitryl.    (&.)  For  the  hydrate  of  (S08)". 

4.  Why  are  there  no  acid  nitrates  ? 

5.  (a.)  Write  the  symbols  of  the  most  common  oxygen  and  hydro- 
gen compounds  with  elements  of  the  chlorine  group.    (&.)  Give  the 
quantivalence  of  each  element,    (c.)  State  the  gradation  of  physical 
and  chemical  properties  among  these  elements,    (d.)  Give  easy  tests 
for  Cl  and  I. 

6.  (a.)  Give  the  usual  mode  of  liberating  C  I  ,  and  write  out  the 
reaction.     (&.)  Find  what  per  cent,  the  Cl  is  of  the  substance  that 
furnishes  it. 

,     7.    Write  the  reactions  expressing    the  preparation  of    at  least 
5HaS04,  using  not  more  than  two  molecules  of  HN03.  '"' 

8.  When  mercuric  oxide  (HgO)  is  heated,  it  decomposes.     Write 
the  reaction.    (Owing  to  the  high  price  of  HgO,  this  reaction  is  sel- 
dom employed.) 

9.  State7  the  composition  of   water,  both  volumetric  and  gravi- 

m('tric 


146  ACIDS,    BASES,    SALTS,    ETC.  §  I?I 

10.  When  0  is  prepared  from  Mn02,  Mn304  is  formed.    Write  the 
reaction. 

11.  When  a  current  of  HaS  is  passed  through  a  solution  of  a  cer- 
tain salt,  copper  sulphide  (Cu"S)  is  precipitated  with  the  formation 
of  H8S04.    Write  the  reaction. 

12.  You  are  given  NaCI  and  H2S04  and  required  to  fill  ajar  with 
HCI.     Describe  the  process  and  sketch  the  apparatus  you  would  use. 

13.  Complete  the  following  equation  with  the  symbol  for  a  single 
molecule:  Ba08  +  2HCI  =  BaCI8  +.t_  £>: 


-u 

W  6/sT  ^ 


BORON. 

Symbol,  B;  specific   gravity,  2.68;   atomic  weight,  llm.  c.; 
quantkalence,  3. 

172.  Boron. — This  element  may  be  obtained  in  the 
crystalline  form  with  a  specific  gravity  as  given  above. 
These  crystals  are  nearly  as  hard,  lustrous  and  highly  re- 
fractive as  the  diamond.  It  may  also  be  obtained  in  the 
amorphous  form  as  a  soft  brown  powder,  or  in  scales  with 
a  graphite-like  lustre.  It  is  not  found  free  in  nature.  It 
has  one  oxide  (boron  trioxide,  boric  or  boracic  anhydride, 
B203).  Its  most  important  compound  is  borax  (sodium 
pyroborate,  Na2B407),  large  quantities  of  which  are  found 
in  California.  Boron  is  the  only  non-metallic  element 
that  forms  no  compound  with  hydrogen.  It  is  remarkable 
for  its  direct  union  (§  53)  with  nitrogen,  the  union  being 
attended  by  the  evolution  of  light  and  the  product  having 
the  composition,  BN. 

(a.}  It  forms  BCI3,  BF3,  etc. 

Experiment  162. — Heat  some  boric  acid  crystals  (§  173)  in  a  clean 
iron  spoon.  The  heated  crystals  first  melt  and  then  become  viscous 
as  the  H  20  is  driven  off.  Touch  this  mass  with  a  glass  rod  and  draw 
out  the  adhering  mass  into  long  threads.  This  viscous  substance 

is  B,08. 

2H3B03  =  B803  +  3H20. 

Experiment  163.—  Dissolve  6  g.  of  powdered  Na2B4O7  in  15  or  20 
cu.  cm.  of  boiling  H20.  Add  3  or  4  cu.  cm.  of  HCI  or  2  cu.  cm.  of 
H2S04  ;  stir  and  allow  to  cool.  Crystals  of  boric  acid  (H3B03)  will 
be  formed. 


148  BORON.  §  173 

Experiment  164- — Dissolve  a  few  crystals  of  H3B03  in  alcohol. 
Upon  igniting  the  alcohol  and  stirring  the  solution,  the  flame  will  be 
of  a  beautiful  green  color;  or  add  a  little  C2H60  and  H2S04  to  a 
solution  of  Na2B407.  Heat  the  materials  and  ignite  the  vapor  ;  the 
flame  will  be  tipped  with  green. 

173.  Boric  Acid.  — Boric  acid  (orthoboric  acid,  bo- 
racic  acid,  H3B03)  may  be  freed  from  any  borate  by  the 
action  of  almost  any  other  acid,  in  consequence  of  which  it 
is  considered  a  very  feeble  acid.  It  may  be  formed  by  the 
union  of  the  oxide  with  water : 

B203  +  3H20=2H3B03. 

(a.)  Upon  heating  H3B03  to  100°C.  it  is  changed  to  metaboric 
acid:  H3B03  —  H20  =  HB02. 

(6.)  Upon  further  heating  at  140'C.  for  a  longtime,  this  is  changed 
to  pyroboric  acid  :  4HB02  —  H20  =  H2B4O7, 

or,  4H3B03— 5H20  =  H2B407. 

(c.)  The  characteristic  green  color  which  the  acid  gives  to  the 
alcohol  flame  affords  a  convenient  test  for  its  presence. 

(d.)  Native  H3B03  is  found  free  in  the  volcanic  regions  of  Tuscany 
whence  nearly  all  that  is  brought  into  commerce  is  obtained.  Vol- 
canic jets  of  steam,  charged  with  H3B03  issue  into  natural  or  arti- 
ficial ponds  or  lagoons,  the  water  of  which  condenses  the  steam  and 
becomes  charged  with  the  acid.  (Fig.  73.)  Upon  evaporation,  these 
waters  yield  pearly  crystals  of  HSB03. 

These  steam  jets  are  called  suffioni.  Deep  borings  into  the  earth 
have  been  made,  constituting  successful  artificial  suffioni.  Basins  of 
masonry  are  built  at  different  levels  on  a  hill  side,  each  of  which 
surrounds  two  or  three  wffioni.  Water  from  a  spring  or  lagoon  is 
conducted  into  the  upper  basin  and  is  charged  by  the  sujfioni  for 
twenty-four  hours.  This  water  is  then  conducted  by  a  wooden  pipe 
to  a  second  basin,  where  it  is  further  charged,  and  so  on  through  six 
or  eight  basins,  when  the  H20  contains  two  or  three  per  cent,  of 
H3B03.  From  the  last  basin,  a  thin  sheet  of  the  liquid  is  run  over 
a  corrugated  sheet  of  lead,  125  m.  long  and  2  m.  wide.  This  lead 
sheet  is  heated  by  the  suffioni  below  it ;  the  liquid  is  thus  eco- 
nomically concentrated  by  evaporation.  The  liquid  is  further  con- 
centrated by  evaporation  in  lead  pans  until  the  acid  begins  to  crys- 
tallize. These  lagoons  produce  about  1,500  Kg.  of  H3BO8  daily. 


L, 


EXERCISES. 

1.  What  is  the    molecular 
weight  of  boron  trioxide?  ^J 0 
y$.  What  per  cent,  of  B  in 
orthoboric  acid  ?  /  7  "^ 

3.  Write  the  symbol  of  cal- 
cium (Ca")  pyroborate.^  fty  I 

4.  (a.)  What  is  the  basicity 
ofH8B03?  (&.)  IsMg3(B03)3 
an  acid  or  a  double  salt  ? 

5.  (a.)   What  results  from 
heating  H3S04  with  Cu,  NaCI 
and   Mn02  respectively?    (&.) 
If  the  latter  two  are   acted 
upon  together,  what  results  ? 

6.  How  much   Zn  must  be 
used  to  generate  sufficient    H 
to  raise  in  the  air,  by  its  buoy- 
ancy,    a     balloon    weighing 

7.  By  strongly  heating  Mn02, 
it  is  reduced  to  a  lower  oxide, 

thus : 

3Mn03  =  Mn304  +  03. 

(a.)  What  weight  and  (&.) 
what  volume  of  0  can  be 
thus  prepared  from  50  g.  of 


8.  State  the  method  of  pre- 
paring HN03  and  the  amount 
of  each  substance   needed  for 
10  Ib.  of  the  acid./  ;.»A        ^     / 

9.  \Vrite  a  graphic  symbol 

for  HP'/r03;  for  HP03. 

(10.)  (a.)  What  is  a  salt? 
How  is  it  formed?  (6.)  How 
does  a  chloride  differ  from  a 
chlorate  ?  Illustrate  by  potas 
sium  compounds. 

11.  (a.)  What  is  the  weight 


FIG.  73- 


"•*'••     SI73 

of  the  C  I  in  5  Ib.  of  common  salt  ?    (6.)  What  per  cent,  of  0  is  there 
in  potassium  chlorate  ? 

12.  Give  the  economic  properties  of  chlorine,  and  show  on  what 
they  depend. 

13.  Give  two  of  the  most  useful  compounds  of  HN03  with  some 
use  of  each.        /i/yi 

14.  Sulphur  trioxide  may  be  obtained  by  heating  concentrated 
H8SO4  with  P806.    Write  the  reaction. 


XII. 


VOLUMETRIC. 

174.  A  Deduction.    Let  us  imagine  such  a  fraction- 
al part  (about  -,  see  §  62)  of  a  liter  of  hydrogen,  that 


it  shall  contain  1,000  hydrogen  molecules.  By  Ampere's 
law,  the  same  volume  of  chlorine  will  contain  1,000 
chlorine  molecules.  By  the  direct  union  of  these  (§  108),  we 
shall  have  formed  two  such  volumes  (about  ~  I.)  of  hydro- 
chloric acid  gas,  which,  according  to  Ampere's  law,  must 
contain  2,000  molecules. 

1000  H2  +  1000  CI2  =  2000  HCI. 

But  each  molecule  of  hydrochloric  acid  (HCI)  contains 
one  hydrogen  atom  and  one  chlorine  atom.  Consequently, 
the  2,000  acid  molecules  will  contain  2,000  Jiydrogen  atoms 
and  2,000  chlorine  atoms.  Since  these  2,000  hydrogen 
atoms  of  the  product  are  identical  with  the  1,000  hydrogen 
molecules  of  the  factor,  it  follows  that  each  hydrogen  mole- 
cule contains  two  atoms  or  that  the  hydrogen  molecule 
is  diatomic.  In  the  same  way  we  see  that  the  chlorine 
molecule  is  diatomic. 

175.  The  Unit  Volume.  —  As  the  weight  of  the 
hydrogen  atom  is  taken  as  the  standard  of  atomic  weight 
and  called  a  microcrith,  so  the  volume  of  the  hydrogen 
atom  is  taken  as  the  standard  of  atomic  volume  and  called 
the  unit  volume.  At  present,  the  absolute  value  of  the 


152  VOLUMETRIC.  §  1  75 

unit  volume  is  as  unknown  as  the  absolute  value  of  the 
microcrith.  The  accurate  determination  of  the  one  will 
carry  with  it  the  determination  of  the  other  (§  62).  The 
unit  volume  is  the  volume  of  one  atom  of  hydro- 
gen; it  is  a  real  unit  measuring  a  definite  quan- 
tity of  matter.  The  (gaseous)  molecular  volume  is  al- 
ways two  unit  volumes. 

(a.}  The  symbols  of  the  diatomic  elements  (§  65)  represent  one  unit 
volume  and  the  respective  atomic  weights  of  the  several  substances  ; 

<•  *'  °  =  1  1  u6nit  Volume  \  of  ox^en'  The  s^mbols  of  tlie  mo"- 
atomic  elements  represent  two  unit  volumes  and  the  respective  atomic 

weights  of  those  substances  ;  e.g.  ,  Hg  =  j  g  ^^i'uSis  }  of  mer- 


cury.    The  symbols  of  the  tetratomic  elements  represent  one-half 
unit  volume  and  the  respective  atomic  weights  of  these  substances  ; 

<•  *->  ?  -  |  i8un?t'  volume}  of  phosphorus.    See  §  240,  e. 

176.  Law  of  Gay-Lussac.—  The  ratio  in  which 
gases  combine  by  volume  is.  always  a  simple  one  ; 
the  volume  of  the  resulting  gaseous  product  bears  a 
simple  ratio  to  the  volumes  of  its  constituents  (see 
§91). 

(a.}  The  following  modes  of  volumetric  combination  illustrate  the 
truth  and  meaning  of  the  law. 

(1.)  1  unit  volume  +  1  unit  volume  =  2  unit  volumes. 
E.g.,  HCI;  HBr;  HI;    NO. 
Condensation  =  0. 

(2.)  2  unit  volumes  +  1  unit  volume  =  2  unit  volumes. 

E.g.,  H20;  H2S;  N20;  N02. 

Condensation  =  i. 

(3.)  3  unit  volumes  +  1  unit  volume  =  2  unit  volumes. 
Kg.,  H,N  ;  S03. 
Condensation  =  £. 


§  176  VOLUMETRIC.  153 

/  00- A 

EXERCISES.     // 

1.  (a.)  What  is  a  unit  volume?    (ft.)  A  microcritli ?    (c.)  What  is 
the  relation  of  specific  gravity  ta   combining  weight?      (d.}  Give 
the  specific  gravity  ofHCI,NH3,CI,  and  C02.   - 

2.  How  could  you  prove  from  a  molecule  of  steam  that  the  mole- 
cules of  0  and  H  have  each  two  atoms  ? 

3.  (a.)  How  is  0  prepared  in  large  quantities?    (6.)  Give  the  reac- 
tion. 

4.  (a.)  Name  three  physical  properties  of  0.     (&.)  Two  chemical 
properties,     (c.)  How  can  these  chemical  properties  be  shown  ?    (d.) 
Mention  one  use  of  0  in  the  arts,    (e.)  One  use  in  the  natural  world, 
(/.)  Mention  three  of  its  most  important  compounds. 

5.  (a.)  Explain  what  is  meant  by  the  atomic  weights  of  H  and  0. 
(&.)  Explain  the  terms  atom  and  molecule  as  applied  to  H20. 

6.  (a.)  If  180  cu.  cm.  of  NH3  be  decomposed  by  electric  sparks  into/'' 
its  elements,  what  will   be  the  volume  of  each  of  these  elements? 
(&.)  If  then  130  cu.  cm.  of  0  be  introduced  and  another  electric  spark 
produced  in  the  containing  vessel,  the  temperature  being  16°C.,  what 
will  be  the  volume  of  the  remaining  gaseous  contents  of  the  vessel  ? 

7.  (a.)  Name  two  chemical  properties  of  H  that  are  the  reverse  of 
two  of  0. 

8.  (a.)  How  is  HN03  prepared  on  a  large  scale?    (&.)  How  can  you 
show  that  an  acid  is  an  acid  ?    (c.)  What  are  alkalies  ?    (d.)  What  is 
"  laughing  gas"?    (e.)  Name  three  oxides  of  N. 

9.  (a.)  What  are  bases?    (6.)  What  class  of  elements  forms  acids? 
(c.)  What  class  of  elements  forms  bases  ?    (d.)  What  is  a  salt  ? 

10.  (a.}  What  is  the  combining  weight  of  a  chemical  compound  ? 
(&.)  HN.OS  +  KhfO  =  KN03  +  H20.     What  is  the  relative  amount  of 
the  substances  used  ? 

11.  Give  the  most  remarkable  chemical  properties  of  Cl  and  I  and 
their  industrial  applications. 

12.  (a.}  Where  is  S  found?    (&.)  How  is  H2S  made,  and  what  are 
its  properties  ?    (c.)  What  is  meant  by  oxidizing  agents  and  what  by 
reducing  agents? 

13.  When  a  thin  stream  of  H2S04  flows  into  a  retort  filled  with 
broken  bricks  hjeated  to  redness,  the  following  reaction  takes  place  : 

$$£&.       '        H,S04  =  SO.  +  H.O  +  0. 

(a.)  What  weight  and  (&.)  what  volume  of  0  can  be  thus  prepared 
from  50 g.  of  H2$04>  C. P.I    (C.  P.  =  chemically  pure,) 

14.  Mn03  and  HCI  are  heated  together.    Give  the  properties  of  the 
gas  evolved. 


154  VOLUMETRIC. 

—  15,  Write  the  symbol  for  the  hydrate  of  sulphuryl. 

16.  (a.)  A  small  quantity  of  H2S04  is  poured  upon  Zn  in  a  flask. 
Give  the  chemical  reaction.    (6.)  Substitute  HCI  for  the  hLSO^  ;  in- 
dicate the  resultant  change,  if  any.    (c.)  If  iron  be  substituted  for 
Zn,  what  change  ? 

17.  How  many  liters  of  Cl  may  be  prepared  from  87. G  g.  of  HCI  ? 

18.  What  weight  of  each  substance  must  be  used  to  prepare  120 
*.ofH2S?J^£,fy/  .  F£$ 

19.  How  much  H2S04  will  dissolve  120  g.  of  Zn?      7f#  f 

20.  Describe  the  preparation  of  HCI,  NH3,  and  N2O.  "'Give  the  re- 
action in  each  caso.     Name  a  chemical  property  of  each. 

21.  (a.)   What  is  the  difference  between  chemical   and  physical 
properties  ?    (&.)  What  is  an  element  ?    (c.)  What  is  a  chemical  com- 
pound  ? 

22.  (a.)  What  is  the  composition  of  air  ?    (6.)  Is  the  air  a  chemical 
compound? 


'V  ~f 


;  /f  i  •-        . 


/   /W°   V  «*       /  «-          /       f*A 

J  i  H-Jfy 

/    •         f)    *  c^yC.' 

' 

X 


THE    CARBON     GROUP. 


I. 


CARBON. 

Symbol,  C  ;  atomic  weight,  12  m.  c.  ;  quantivalence,  4. 

177.  Occurrence.—  Two  allotropic  modifications  of 
carbon,  the  diamond  and  graphite,  are  found  free  in 
nature.  Carbon  is  also  found  free  in  an  impure  form,  as 
mineral  coal.  Combined  with  hydrogen,  it  occurs  in  pe- 
troleum, bitumen,  etc.  Combined  with  oxygen,  it  forms 
a  constituent  of  the  atmosphere  upon  which  all  vegetable 
life  is  directly  dependent.  United  with  oxygen  and  cal- 
cium, it  is  found  as  limestone,  chalk  and  marble.  All 
organic  bodies  contain  carbon  and  when  any  of  these  is 
heated  out  of  contact  with  oxygen  there  remains  a  third 
allotropic  variety,  amorphous  carbon  or  charcoal.  Cer- 
tainly, carbon  is  a  very  abundant  and  important  element. 

(a.)  The  chemical  identity  of  these  several  allotropic  forms  is 
shown  by  the  fact  that,  when  highly  heated  with  0,  they  all  form 
the  same  compound,  C02,  12  parts  of  any  variety  of  C  uniting 
with  32  parts  of  0  to  form  44.  parts  of  the  oxide. 

Experiment  165.—  Arrange  the  apparatus  as  shown  in  Fig.  74. 
Two  thick  copper  wires  pass  through  a  caoutchouc  stopper  that 
closes  the  mouth  of  a  cylinder  filled  with  0.  The  enclosed  ends  of 
the  copper  wire  are  joined  by  a  spiral  of  fine  platinum  wira.  Place 


156  CARBON.  §  178 

a  small  diamond,  if  you  have  one  to  spare,  in  the  spiral  at  a,  and 
pass  the  electric  current  from  a  battery  of 
eight  Grove's  cells  through  the  wires.  The 
platinum  is  heated  to  whiteness  and  the  dia- 
mond takes  fire.  On  breaking  the  circuit, 
you  will  see  a  brilliant  combustion  result- 
ing in  the  complete  disappearance  of  your 
diamond.  If  a  small  quantity  of  clear  lime 
water  has  been  previously  placed  in  the 
cylinder,  it  will  remain  clear  until  the  dia- 
mond has  burned.  Upon  agitating  the 
lime  water,  at  the  close  of  the  combustion, 
it  will  be  rendered  milky  in  appearance, 
thus  showing  the  formation  of  C02.  See 
Exp.  44. 
FIG.  74. 

178.  The  Diamond.  —  Diamond  is  a  crystalline 
solid,  brilliant,  transparent  and  generally  colorless.  Dia- 
monds are  most  frequently  found  in  the  form  of  rounded 
pebbles  and  cut  into  the  desirable  forms  by  pressing  the  sur- 
face of  the  stone  against  a  revolving  metal  wheel  covered 
with  a  mixture  of  diamond  dust  and  oil,  diamond  being 
the  only  substance  hard  enough  to  cut  the  gem.  Thus, 
we  see  that  it  is  the  hardest  known  substance.  It  does 
not  conduct  heat  or  electricity  and,  when  polished,  has  a 
magnificent  lustre  and  high  refractive  power  upon  light 
(Ph.,  §  613,  a.).  These  properties,  together  with  its  perma- 
nence and  rarity,  make  it  the  most  precious  of  gems.  Its 
specific  gravity  is  3.5.  One  of  the  long  standing  prob- 
lems of  chemistry  has  recently  been  solved  by  the  produc- 
tion of  artificial  diamonds. 

(a.)  The  diamond  undergoes  no  change  at  the  ordinary  tempera- 
ture, but,  when  heated  between  the  carbon  electrodes  of  a  strong 
electric  current,  it  softens,  swells  up  and  is  changed  to  a  black  mass 
resembling  coke.  When  heated  in  0,  it  burns  to  C02,  as  explained 
in  Exp.  165.  In  hydrogen  or  any  atmosphere  that  has  no  chemical 


§  l8l  CARBON.  157 

action  upon  it,  the  diamond  may  be  heated  to  the  highest  furnace 
temperature  without  change.  "  The  Regent "  diamond  is  valued  at 
£125,000. 

179.  Graphite. — Graphite  or  plumbago  is  familiarly 
known  as  the  "  black-lead"  of  the  common  "  lead  pencil." 
It  is  found  abundantly  in  nature  in  the  crystalline  and 
amorphous  forms,  the  crystals  being  wholly  unlike  those 
of  the  diamond.  It  is  opaque,  nearly  black,  and  has  a 
semi -metallic  lustre.  It  is  very  friable  and  has  an  unctu- 
ous feel.  It  is  a  good  conductor  of  heat  and  electricity. 
It  is  unalterable  in  the  air  at  ordinary  temperatures.  Its 
specific  gravity  varies  from  2  to  2.5.  It  is  used  in  making 
pencils,  lubricating  machinery,  in  making  crucibles  es- 
pecially for  the  manufacture  of  steel,  as  a  stove  polish  and 
in  electro  typing  (Ph.,  §  400). 

(a.)  For  many  years,  graphite  was  supposed  to  contain  lead  ; 
whence  the  names  plumbago  and  black-lead.  The  name,  graphite, 
is  from  the  Greek  word,  grapho,  (  =  I  write). 

1§O.  Intermediate  Forms. — Intermediate  between  graph- 
ite and  charcoal  are  the  forms  of  carbon  known  as  mineral  coal,  coke 
and  gas  carbon. 

181.  Mineral  Coal. —  Mineral  coal  consists  of  the 
remains  of  the  vegetation  of  the  carboniferous  era  in  the 
earth's  geologic  history.  The  woody  fibre  has  undergone 
a  wonderful  transformation  through  the  means  of  heat  and 
pressure.  When  a  considerable  part  of  the  hydrogen, 
oxygen  and  nitrogen  of  the  original  woody  material  re- 
mains in  this  product,  the  coal  is  called  soft  or  bituminous. 
These  elements  may  be  largely  removed  from  bituminous 
coal  by  distillation.  Soft  coal  generally  contains  sulphur 
impurities  and  cakes  in  burning.  When  the  coal  has  been 
subjected  to  a  sort  of  natural  distillation,  so  that  it  has 


158  CARBON.  §  l8l 

been  deprived  of  nearly  all  of  its  hydrogen,  oxygen  and 
nitrogen,  it  is  called  hard  coal  or  anthracite.  •  There  is  a 
somewhat  complete  gradation  of  coals  from  anthracite 
down  to  lignite  and  peat,  in  which  the  wood  is  but  little 
changed. 

Experiment  166.—  Half  fill  a  good  sized  ignition  tube  (one  about 
15  cm.  long  will  answer  well)  with  coarsely  powdered  bituminous 
coal.  Close  its  mouth  with  a  cork  carrying  a  delivery  tube  made  of 


FIG.  75. 

good  sized  glass  tubing  that  terminates  in  a  water  bath.  Support 
the  ignition  tube  in  a  sloping  position  and  heat  the  coal.  Collect  the 
gas  in  small  bottles  as  it  is  delivered  in  the  water  bath.  The  gas 
will  burn  as  if  it  were  ordinary  illuminating  gas.  When  the  igni- 
tion tube  has  cooled,  break  it  and  examine  the  coke  that  it  contains. 

182.  Coke. — When  bituminous  coal  is  distilled,  it 
yields  a  variety  of  volatile  hydrogen-carbon  compounds 
(hydrocarbons)  and  a  solid,  porous  residue  called  coke. 
The  latter  is  an  incidental  product  of  the  manufacture  of 
illuminating  gas  but  is  also  made  on  a  large  scale  for  use 
in  iron  smelting,  the  volatile  constituents  of  the  coal  being 
allowed  to  escape.     (§  221,  #.) 

183.  Gas  Carbon.—  Gas  carbon  is  a  very  hard,  com- 
pact substance  that  is  formed  as  a  crust  on  the  inner  sur- 


§  184  CARBON.  159 

face  of  the  retorts  at  gas  works.  It  is  a  good  conductor 
of  heat  and  electricity  and  is  largely  used  in  the  manu- 
facture of  galvanic  batteries  (Ph.,  §§  383,  385)  and  of  the 
carbon  electrodes  of  electrie  lamps  (Ph.,  §  389.). 

Experiment  167.— Repeat  Exp.  166,  using  splinters  or  shavings  of 
wood  instead  of  soft  coal.  When  the  gas  is  no  longer  evolved,  re- 
move the  end  of  the  delivery  tube  from  the  water  pan  and  imbed  it 
in  a  thick  paste  of  plaster  of  Paris  to  prevent  the  entrance  of  air  to 
the  ignition  tube.  When  the  apparatus  has  cooled,  the  charcoal 
may  be  removed  without  breaking  the  tube. 

Experiment  1GS. — Heat  a  piece  of  charcoal  upon  platinum  foil  and 
notice  tliat  it  burns  with  a  simple  glow,  i.e.,  without  any  flame. 

184:.  Charcoal. — Charcoal  is  generally  prepared  by 
the  distillation  or  incomplete  combustion  of  wood.  In 
England,  where  wood  is  scarce,  small  wood  and  saw-dust 
are  distilled  in  cast  iron  retorts,  the  volatile  products  being 
collected.  In  this  country,  where  wood  is  yet  abundant, 
the  process  is  more  primitive,  the  volatile  products  gener- 
ally going  to  waste. 

(d.)  The  common  method  of  burning  charcoal  is  to  pile  up  sticks 
of  wood  in  a  large  heap  around  a  central  flue,  covering  it  with  turf 

a 


FIG.  76. 

and  earth,  leaving  holes  at  the  bottom  for  the  admission  of  air  and 
a  hole  at  the  top  of  the  central  flue.     The  fire  is  kindled  at  the  hot- 


160 


CARBON 


§184 


torn  of  the  central  flue,  and  the  rate  of  combustion  controlled  by 
regulating  the  supply  of  air,  the  process  often  requiring  several 
weeks.  At  the  proper  time,  all  of  the  openings  are  closed  and  the 
fire  thus  suffocated.  The  method  depends  upon  the  fact  that  the 
volatile  constituents  of  the  wood  are  more  easily  combustible  than 
the  C  and  thus  unite  with  the  limited  supply  of  0.  In  some  parts 
of  the  country,  charcoal  is  burned  in  permanent  kilns,  instead  of 
turf  covered  heaps. 

(6.)  The  charcoal  retains  the  form  of  the  wood  from  which  it  was 
made,  the  shape  of  the  knots  and  even  the  concentric  rings  being 
plainly  visible.  Its  volume  is  about  65  or  70  per  cent,  and  its  weight 
about  25  per  cent,  of  the  wood  from  which  it  was  formed. 

Experiment  169.— Set  fire  to  a  lump  of  rosin  and  hold  a  cold  plate 
over  the  flame.  Soot  will  be  deposited  upon  the  plate. 

Experiment  170.  —  Press  a  spoon  or  plate  down  upon  a  candle 
flame  so  as  nearly  to  extinguish  the  flame. 
Soot  will  be  deposited  upon  the  spoon. 

Experiment  171.  —  Partly  fill  a  spirit 
lamp  with  turpentine,  light  the  wick  and 
cover  the  lamp  with  a  bell  glass  or  wide 
mouthed  jar.  Thrust  a  pencil  or  chalk 
crayon  under  one  edge  of  the  bell  glass  so 
as  to  raise  it  from  the  table  and  admit  a 
small  supply  of  air  to  the  flame.  Soot 
will  collect  upon  the  sides  of  the  bell 
glass. 

185.  Lampblack.  —  When  a 
FIG.  77.  hydrocarbon,  like  rosin,  turpentine, 

wax,  petroleum,  etc.,  is  burned,  the  hydrogen  is  first  oxidized. 
If  the  supply  of  oxygen  be  insufficient  for  the  complete 
combustion,  the  carbon  set  free  by  the  decomposition  of 
the  compound  will  be  left  in  a  finely  divided,  amorphous 
state,  as  soot  or  lamp-black.  The  same  effect  will  appear 
if  the  temperature  of  the  flame  be  reduced  below  that  at 
which  carbon  burns,  as  was  the  case  in  Exp.  1G9.  Lamp- 
black is  manufactured  on  the  large  scale  by  burning  tar. 


§  187  CARBON.  161 

rosin,  turpentine,  petroleum,  or  the  natural  gases  of  petro- 
leum (gas  wells)  in  a  supply  of  air  insufficient  for  complete 
combustion  and  leading  the  smoky  products  into  large 
chambers,  where  they  are  deposited.  It  is  largely  used  as 
a  pigment  and  in  the  manufacture  of  india  and  printer's 
inks. 

186.  Bone-black. — Bone-black,  which  is  the  most 
important  variety  of  "animal  charcoal,"  is  prepared  by 
charring  powdered  bones  in  iron  retorts.     The   calcium 
phosphate  of  the  bone  remains  and  ;forms  about  90  per 
cent,  of  the  black  porous  mass.     The  charcoal  is  conse- 
quently left  in  a  very  finely  divided  or  porous  condition, 
spread   over  the   particles  of  the  phosphate  or  distrib- 
uted among  them.     For  this  reason,  it  has  greater  ab- 
sorptive and  decolorizing  power  than  vegetable  charcoal 
(Exp.  180). 

Experiment  172 .— Mix  2.5 g.  of  black  copperoxide  (CuO)  with  0.25  #. 
of  powdered  charcoal.  With  some  of  the  mixture,  partly  fill  a  small 
ignition  tube  and  heat  it  strongly.  Metallic  copper  will  remain  in 
the  tube  while  the  C  will  unite  with  the  0  of  the  CuO  and  escape  as 
a  gas.  The  C  has  reduced  the  CuO  and  the  CuO  has  oxidized  the  C. 

187.  Charcoal  as  a  Reducing  Agent. — Owing 
to  the  energetic  union  of  carbon   and  oxygen  at  high 
temperatures,  charcoal  is  largely  used  as  a  reducing  agent. 
Anthracite  and  coke  are  also  used  for  the  same  purpose. 
The  preparation  of  metals  from  their  ores  (metallurgy)  de- 
pends in  a  very  large  degree  upon  this  property  of  carbon. 

Experiment  173.— Break  a  piece  of  charcoal  into  two.  Attach  a 
sinkei  to  one  of  the  fragments  and  immerse  it  in  H.,0.  Notice  the 
bubbles  rise  as  the  H20  enters  the  pores  of  the  charcoal  and  forces 
out  the  air  previously  absorbed.  The  experiment  may  be  improved 
by  placing  the  beaker  glass  containing  the  H20  and  the  C  under  the 
receiver  of  an  air  pump  and  exhausting  the  air. 

Experiment  174. — Place  the  other  fragment  of  the  charcoal  on  the 


162  CARBON.  §  188 

fire,  and  when  it  has  been  heated  to  full  redness  for  some  time, 
plunge  it  quickly  into  H20.  Notice  that  it  needs  no  sinker  to  keep 
it  under  H20  and  that  very  few  bubbles  escape  from  it  through  the 
liquid. 

Experiment  175. — Fill  a  long  glass  tube  with  dry  NH3  at  the  mer- 
cury bath  (Exp.  61).  Heat  a  piece  of  char- 
coal to  redness  to  remove  the  air  from  its 
pores  and  plunge  it  into  mercury.  When 
the  charcoal  is  cool,  thrust  it  into  the 
mouth  of  the  cylinder.  The  gas  will  be 
absorbed  by  the  charcoal  and  mercury 
will  rise  in  the  tube  (Ph.,  g  275). 

Experiment  176.— Repeat  the  last  experi- 
ment, using  dry  HCI  instead  of  NH3. 

188.  Charcoal  as  an  Absorbent.— The  porous 
nature  of  charcoal  gives  it  a  remarkable  power  of  absorb- 
ing gases.  Beech  wood  charcoal  has  been  known  to  ab- 
sorb 170  times  its  own  volume  of  dry  ammonia.  Other 
gases,  liquefiable  with  comparative  readiness  (e.  g.,  HCI, 
S02,  H2S,  N20,  CC>2)  are  absorbed  in  large  but  variable 
proportions,  while  gases  that  are  coercible  only  with  diffi- 
culty (e.g.,  0,  H  and  N)  are  absorbed  much  more  spar- 
ingly. 

This  power  depends  upon  the  fact  that  all  gases  condense 
in  greater  or  less  degree  upon  the  surface  of  solid  bodies 
with  which  they  come  into  contact.  It  is  said  that  1  cu.  cm. 
of  compact  (boxwood)  charcoal  exposes  a  surface  of  0.5  sq.  m. 
The  more  easily  the  gas  is  liquefied  the  more  largely  is  it 
absorbed  by  charcoal,  which,  at  least,  points  toward  the 
conclusion  that  in  such  absorption  it  is,  at  least,  partly 
liquefied. 

Experiment  177. — Into  a  bottle  of  H,S  put  some  powdered  char- 
coal .  Shake  the  bottle  for  a  moment .  The  offensive  odor  of  the  H  2 S 
will  have  disappeared. 

Experiment  178. — Into  the  neck  of  a  funnel,  thrust  a  bit  of  cotton 


§igo 


CARBON. 


163 


woo]  and  cover  it  to  the  depth  of  2  or  3  cm.  with  powdered  charcoal. 
Through  this  solution,  pass  a  quantity  of  H2O  charged  with  H2S 
(§  138,  «.)•  The  filtered  liquid  will  be  free  from  offensive  odor. 

Experiment  179. — Place  a  small  crucible  filled  with  freshly  ignited 
and  nearly  cold  powdered  charcoal  into  ajar  kept  supplied  with  H2S. 
When  the  charcoal  is  saturated  with  the  gas,  quickly  transfer  it  to 
a  jar  of  0.  The  charcoal  will  burst  into  vivid  combustion. 

189.  Charcoal  as  a  Disinfectant. — By  condens- 
ing offensive  and  injurious  gases  and  bringing  them  into 
intimate  contact  with  condensed  oxygen,  charcoal  acts  as 
an  energetic  disinfectant.     The  fetid  products  of  animal 
and  vegetable  decay  are  not  only  gathered  in  but  actually 
burned  up.     This  property  is  retained  by  the  charcoal  for 
a  long  time  and,  when  lost,  may  be  restored  by  ignition. 
A  dead  animal  may  be  buried  under  a  thin  covering  of 
charcoal  and  waste  away  without  giving  off  any  offensive 
odor.     This  oxidizing  power  of  charcoal  fits  it  for  use  as  a 
disinfectant  in  hospitals,  dissecting  rooms  and  elsewhere, 
and  forms  the  foundation  of  much 

of  the  utility   of  charcoal  filters 
for  water  for  drinking  purposes. 

Experiment  180. — Place  a  dilute  solu- 
tion of  the  blue  compound  of  iodine 
and  starch  (Exp.  121),  of  indigo  dis- 
solved in  H2S307  (§  156),  of  cochineal  and 
of  potassium  permanganate  in  each  of 
four  flasks  To  each ,  add  recently  ignited 
bone-black.  Cork  the  flasks,  shako 
their  contents  vigorously,  and  pour  each 
liquid  upon  a  separate  filter.  The  sev- 
eral filtrates  will  be  colorless.  If  the 
first  part  of  any  filtrate  be  colored,  pour 
it  back  upon  the  filter  for  refiltration.  FIG.  79. 

190.  Charcoal  as  a  Decolorizer.— As  illustrated 
in  the  above  experiment,   charcoal,  and  especially  animal 


164  CARBON.  §  IQO 

charcoal  or  bone-black,  is  able  to  remove  the  color  as  well 
as  odor  from  many  solutions.  This  power  seems  to  de- 
pend more  upon  the  adhesion  between  the  carbon  and  the 
particles  of  coloring  matter  than  upon  oxidation.  Brown 
sugar  is  purified,  by  filtering  its  colored  solution  through 
layers  of  bone-black.  If  ale  or  beer  be  thus  treated,  it 
loses  both  its  color  and  bitter  taste.  Thus  we  see  that 
charcoal  can  remove  other  substances  than  coloring  matter 
from  solutions.  Sulphate  of  quinine  and  strychnine  may 
be  thus  removed.  This  property  of  charcoal  (and  bone- 
black)  is  utilized  in  the  preparation  or  purification  of  many 
chemical  or  pharmaceutical  compounds. 

191.  Other  Properties  of  Carbon. — Carbon,  in 
all  of  its  forms,  is  practically  infusible  and  non-volatile, 
but  it  may  be  slightly  fusible  and  volatile  at  the  high  tem- 
perature of  the  voltaic  arc.  Although  it  has  great  chemi- 
cal activity  at  high  temperatures,  it  seems  to  be  unalter- 
able at  the  ordinary  temperature  of  the  air.  The  lower 
ends  of  stakes  and  fence  posts  are  often  charred  before 
embedding  them  in  the  earth  to  render  them  more  durable. 
Charred  piles  driven  in  the  River  Thames  by  the  ancient 
Britons  in  their  resistance  to  the  invasion  of  their  country 
by  Julius  Caesar,  about  54  B.  C.,  are  still  well  preserved. 
Wheat,  charred  at  the  destruction  of  Herculaneum  and 
Pompeii,  in  79  A.D.,  still  appears  as  fresh  as  if  recently 
prepared.  Perfectly  legible  manuscripts,  written  in  ink 
made  of  lamp-black,  have  been  exhumed  with  Egyptian 
mummies.  Carbon  is  unique,  in  that  it  forms  a  very  large 
number  of  volatile  hydrogen  compounds.  These  com- 
pounds are  called  hydrocarbons. 

Note.—  Binary  compounds  of  carbon  were  formerly  called  car- 
burets. 


§  IQI  CARBON.  165 


EXEECISES. 

1.  Is  charcoal  lighter  or  heavier  than  H20  ? 

2.  (a.)  I  burn  a  piece  of  wood  in  the  open  air  ;  what  becomes  of  it? 
(b.)  What  volume  of  steam  will  result  from  burning  100  g.  of  H  ? 

3.  (a.)  State  the  useful  properties  of  charcoal.     (&.)  How  much  0 
is  needed  to  burn  500  g.  of  charcoal  ?     (c.)  How  many  liters  of  CO., 
will  be  produced?    /3  ^ 

4.  Give  the  characteristics  of  three  allotropic  modifications  of  car- 
bon, and  give  a  leading  property  of  each. 

5.  How  would  you  prepare  a  solution  of  HCI  ? 

6.  Write  the  symbol  for  sulphuryl  oxide.       ^ 

7.  Write  the  typical  and  empirical  symbols  ?or  nitrosyl  hydrate 
and  nitryl  hydrate. 

8.  Write  the  reaction  for  the  combustion  of  turpentine  in  Exp.  93. 

9.  Give  proof  of  the  fact  that  diamond  is  carbon. 

10.  In  what  way  does  the  disinfecting  power  of  C  differ  from  that 
of  Cl  ? 

11.  Is  C  a  bleaching  agent  ?    Why? 

12.  Would  it  not  be  a  great  improvement  in  quinine  to  filter  it 
through  charcoal  and  thus  remove  its  intensely  bitter  taste  ?    Why  ? 

13.  Symbolize  compounds  of  C  with  L',  M"    Q,'"  R  and  X,  these 
last  letters  symbolizing  hypothetical  elements. 

,  iv  iv 

14.  Write  graphic  symbols  for  H8S03  and  H3S03, 

$\\    '  ^ 


0 


166  SOME    CARBON    COMPOUNDS. 


SOME    CARBON    COMPOUNDS. 

192.  Carbon   Oxides.  —  There  are  two  oxides  of 
carbon,  having  the  molecular  symbols  CO  and  C02-     The 
first  may  be  considered  the  product  of  incomplete  combus- 
tion of  carbon  ;  the  second,  that  of  complete  combustion. 
Both  of  them  are  gaseous. 

193.  Carbon  Monoxide.— Carbon  monoxide  (car- 
bon protoxide,   carbonic  oxide,  carbonous  oxide,   carbo- 
nyl,  CO)  yields,  when  burned,  the  characteristic  blue  flame 
often  seen  playing  over  a  freshly  fed  coke  or  anthracite 
fire.      It   may  be  prepared  in  many  ways,  only  two  of 
which  will  be  given  here. 

Experiment  181. — Pulverize  5  g.  of  potassium  ferrocyanide  and 
place  it  in  a  quarter  liter  Florence  flask.  Add  25  cu.  cm.  of  strong 
H2S04  and  heat  gently,  removing  the  lamp  as  soon  as  the  gas  begins 
to  come  off  rapidly.  The  gas  may  be  passed  through  a  solution  of 
potassium  hydrate  (KHO)  and  collected  over  H20. 

Experiment  1S2. — Place  a  small  quantity  of  oxalic  acid  (H2C204) 
in  a  small  Florence  flask,  add  enough  strong  H2S04  to  cover  it,  place 
upon  a  sand  bath  and  heat  gently.  The  H,S04  removes  H20  from 
the  H2C2O4  and  leaves  a  mixture  of  CO  and  C02.  The  C0g  may 
be  removed  by  passing  the  mixed  gases  through  a  solution  of  KHO, 
as  in  the  last  experiment,  or  by  collecting  over  H30  rendered  alka- 
line by  such  a  solution. 

194.  Properties. — Carbon  monoxide  is  a  colorless, 
odorless,  poisonous  gas.     It  is  a  little  lighter  than  air, 
having  a  specific  gravity  of  14  (sp.  gr.  =  .967,  air  stand- 
ard).   It  is  scarcely  soluble  in  water,  but  is  wholly  ab- 
sorbed by  an  acid  or  ammoniacal  solution  of  cuprous 


§  Ip5  SOME    CARBON    COMPOUNDS.  167 

chloride  (Cu2CI2).  It  is  liquefiable  only  with  extreme 
difficulty.  Like  hydrogen,  it  does  not  support  combus- 
tion but  is  combustible.  It  burns  with  a  pale  blue  flame 
and  yields  carbon  dioxide  (C02)  as  the  sole  product  of  its 
combustion.  It  is  an  active  pouon  and  doubly  dangerous 
on  account  of  its  lack  of  odor.  One  per  cent,  of  it  in  the 
air  is  fatal  to  life,  which  it  destroys,  not  merely  by  exclud- 
ing oxygen  (suffocation),  as  hydrogen,  nitrogen,  etc.,  do, 
but  by  direct  action  as  a  true  poison.  As  this  gas  is 
formed  in  charcoal  and  anthracite  fires,  and  as  it  secures 
an  easy  passage  through  faulty  joints  and  even  through  cast 
iron  plates  heated  to  redness,  it  is  the  frequent  cause  of 
oppression,  headache  and  danger  in  stove  or  furnace- 
heated  and  ill-ventilated  rooms.  Carbon  monoxide  is 
rightly  chargeable  with  many  of  the  ill  effects  usually  at- 
tributed to  the  less  dangerous  carbon  dioxide. 

(a.)  CO  is  readily  oxidized  to  C02  and  C02  is  easily  reduced  to 
CO.  Thus,  when  air  enters  at  the  bottom  of  an  anthracite  fire,  the 
0  unites  with  the  C  to  form  C02.  As  the  C03  rises  through  the 
glowing  coals  above,  it  is  reduced  to  CO.  CO2  +  C  =  SCO.  When 
this  heated  CO  comes  into  contact  with  the  air  above  the  coals,  it 
burns  with  its  characteristic  blue  flame  and  forms  C02. 

(&.)  Under  the  influence  of  sunlight,  two  volumes  of  CO  unite 
'directly  with  two  volumes  of  Cl,  forming  two  volumes  of  carbonyl 
chloride  or  phosgene  gas  (COCU).  It  will  be  noticed  that  here,  CO 
acts  as  a  dyad  compound  radical. 

195.  Uses. — Carbon  monoxide  is  an  important  agent 
in  many  metallurgical  operations,  on  account  of  its  power 
to  reduce  metallic  oxides.  It  may  be  used  instead  of  hy- 
drogen in  Exp.  31.  In  the  reverberatory  furnace,  the  air 
supply  is  regulated  so  that  the  fuel  burns  to  carbon  mon- 
oxide, which,  in  a  highly  heated  condition,  plays  over  the 
metallic  oxides  on  the  hearth  and,  by  abstracting  oxygen 


168  SOME    CARBON    COMPOUNDS.  §  195 

from  them  for  its  own  combustion  to  carbon  dioxide,  re- 
duces them  to  the  metallic  condition. 

196.  Carbon  Dioxide.  — Carbon  dioxide  (carbonic 
anhydride,  C02,  often  improperly  called  carbonic  acid  or 
carbonic  acid  gas)  is  always  formed  when  carbon  or  any 
carbon  compound  is  burned  under  conditions  that  afford 
an  abundant  supply  of  oxygen.  It  may  be  easily  obtained 
by  the  decomposition  of  carbonates,  such  as  marble,  chalk, 
or  limestone.  It  is  a  product  of  animal  respiration,  of 
fermentation  and  of  the  decay  and  putrefaction  of  all  ani- 
mal and  vegetable  matter.  It  is  produced  in  large  quan- 
tities in  burning  limestone  to  quicklime. 
CaC03  =  CaO+  C02. 

Experiment  183. — Repeat  Exps.  42  and  44.    The  white  precipitate 
that  causes  the  turbidity  is  calcium  carbonate  (CaC03). 
CaH202  +  C03  =  CaC03  +  H20. 

Experiment  1S4. — Mix  11  g.  of  red  oxide  of  mercury  and  0.3  g.  of 
powdered  charcoal.  Heat  the  mixture  and  collect  over  H2O  the 
gas  that  is  given  off.  Test  the  gas  with  lime  water.  The  0  that 


FIG.  80. 

united  with  the  C  came  from  the  mercury  oxide.  2HgO  +  C  —  CO2 
+  2Hg.  Examine  the  ignition  tube  carefully  for  traces  of  metallic 
mercury.  In  similar  manner,  many  solid,  liquid  and  gaseous  bodies 
that  are  rich  in  0  give  it  up  readily  to  unite  with  C  and  form  C02. 
In  other  words,  such  bodies  are  "  reduced  "  by  the  C- 


§I96 


SOME    CARBON    COMPOUNDS. 


169 


Experiment  185. — Into  a  bottle,  arranged  as  described  in  §  20,  put 
a  handful  of  small  lumps  of  marble  or  chalk  (CaC03).  Prepared 
crayons  mil  not  answer.  Cover  the  lumps  with  H2O  and  add  small 
quantities  of  HCI  from  time  to  time  as  may  be  needed  to  secure  a 
continued  evolution  of  gas.  Collect  several  bottles  of  the  gas  over 


FIG.  81. 


H20. 


Replace  the  tube  d  by  one  bent  downward  at  right  angles 
near  c.  Insert  the  vertical  part  of  this  tube  in  a  bottle.  As  this  gas 
is  heavier  than  air,  it  may  be  collected  thus  by  "  downward  displace- 
ment." 

CaC03  +  2HCI  =  CaCI2  +  H20  +  C02. 

Note.—  HCI  is  better  than  H2S04  in  preparing  CO2  from  CaC03 
because  CaCI2  is  more  easily  soluble  than  CaS04.  Old  mortar, 
powdered  oyster  shells,  coral  or  limestone  will  answer  instead  of 
marble  or  chalk,  but  marble  is  preferable  as  there  is  less  frothing. 

Experiment  186. — Arrange  two 
flasks  containing  lime  water,  as 
shown  in  Fig.  83.  Apply  the  lips 
to  the  tube  and  inhale  and  exhale 
air  through  the  apparatus.  In  a 
few  moments,  the  lime  water  in  C, 
through  which  the  air  passes  from 
the  lungs,  will  b3comemilky,while 
that  in  B,  through  which  the  air 
passes  to  the  lungs,  remains  clear. 
See  Exp.  44.  Unrespired  air  forced 
through  lime  water  by  means  of  a 
small  bellows  or  other  means  will 
not  produce  such  turbidity. 

Experiment  1S7.  —  Dissolve   50 
8 


FIG.  82. 


170 


SOME    CARBON    COMPOUNDS. 


196 


cu.  cm.  of  molasses  in  about  400  cu.  cm.  of  H20  and  place  the  liquid 
in  a  half  liter  flask.  Add  a  few  spoon- 
fuls of  yeast,  cork  the  flask  and  con- 
nect its  delivery  tube  with  a  small  bot- 
tle, b,  filled  with  H  20.  A  delivery  tube 
should  extend  from  the  bottom  of  b 
into  a  cup,  c.  Put  the  apparatus  into 
a  warm  place  and  fermentation  will 
soon  begin.  As  the  liquid  in  F  fer- 
ments, bubbles  of  gas  will  rise  through 
it  and  pass  over  into  &,  forcing  a  cor- 
responding quantity  of  H20intoc.  When  b  is  nearly  full  of  this 
gas,  remove  its  stopper  and  test  its  contents  with  a  flame  and  with 
lime  water.  The  gas  is  C02  (§  200).  Let  the  liquid  in  ^remain  in 
a  warm  place  for  two  or  three  days.  Cork  and  save  for  future  use. 

The  sugar  (C6H1206)  of  the  molasses  was  decomposed  into  alcohol 
(CaH60)  and  C02.    The  C2H60  remains  dissolved  in  the  liquid  in  F. 


FIG.  83. 


FIG.  84. 


Experiment  188. — Suspend  a  light  glass  or  paper  jar  from  one  end 
of  a  scale  beam  and  counterpoise  it  with  weights  placed  in  the  scale 


§  197  SOME    CARBON    COMPOUNDS.  171 

pan    at    the    opposite    end.    Pour    C02    into  the  jar  and  it    will 
descend. 

Experiment  189. — Partly  fill  a  wide  mouthed  jar  with  C02. 
Throw  an  ordinary  soap  bubble  into  the  jar.  It  will  float  on  the  sur- 
face of  the  heavy  gas. 

Experiment  190.— Fill  a  long  necked  Florence  flask  with  C02 .  Pour 
in  a  little  H20,  close  the  mouth  with  cork  or  finger,  shake  the  bot- 
tle and  then  open  the  mouth  under  water.  Part  of  the  C02  will 
have  been  dissolved  in  the  H30,  and  more  H20  will  enter  the  flask 
to  fill  the  partial  vacuum.  Close  the  mouth,  shake  again,  and  once 
more  open  the  mouth  underwater,  More  H20  will  enter.  In  this 
way,  all  of  the  C02  may  be  dissolved  in  H20.  After  agitating  C02 
and  H20  in  a  test  tube  closed  by  the  thumb  or  palm  of  the  hand, 
the  tube  and  contents  may  be  held  hanging  from  the  hand,  supported 
by  atmospheric  pressure.  (Ph.,  §  293.) 

197.  Physical  Properties. — Carbon  dioxide  is  a 
colorless  gas,  so  heavy  that  it  may  easily  be  poured  from 
one  vessel  to  another.  Its  specific  gravity  is  22,  it  being 
1£  times  as  heavy  as  air.  In  consequence  of  its  high 
specific  gravity,  it  diffuses  but  slowly  and  often  accumu- 
lates in  wells,  mines  and  caverns  (see  article,  "  Grotto  del 
Cane,"  in  any  encyclopaedia).  Under  a  pressure  of  50 
atmospheres  at  the  ordinary  temperature,  it  condenses  to 
a  liquid  whose  specific  gravity  is  0.83.  The  rapid  expan- 
sion of  this  liquid,  when  released  from  pressure,  produces 
a  temperature  low  enough  to  freeze  part  of  itself  to  a  white, 
snow-like  mass.  This  solid  carbon  dioxide,  when  mixed 
with  ether,  produces  a  degreo  of  cold  that  quickly  freezes 
mercury,  and  in  a  vacuum,  yields  a  temperature  of — HO^C. 
The  gas  is  soluble  in  water,  volume  for  volume  at  ordinary 
temperatures  and  pressures;  more  largely,  at  lower  tem- 
peratures or  higher  pressures. 

Experiment  191.—  From  a  large  vessel  filled  with  C08,  dip  a  turn- 


172  SOME    CARBON    COMPOUNDS.  £  198 

blerful  of  the  gas  and  pour  it,  as  if  it  were 
H20,  upon  the  flame  of  a  taper  burning 
at  the  bottom  of  another  tumbler.  The 
flame  will  be  extinguished. 

Experiment  192. — Fasten  a  tuft  of  "  cot- 
ton wool"  to  the  end  of  a  wire  or  glass 
rod,  dip  it  into  alcohol,  ignits  and  quickly 
thrust  the  large  flame  into  a  bottle  of 
C02.  The  flame  will  be  instantly  extin- 
FIG.  85.  guished. 

Experiment  193. — Fasten  a  piece  of  magnesium  ribbon,  15  or 
'20  cm.  (6  or  8  in.)  long  to  a  wire,  ignite  the  ribbon  and  quickly 
plunge  it  into  a  jar  of  C02.  It  will  continue  to  burn,  leaving  white 
flakes  of  magnesium  oxide  (MgO)  mixed  with  small  particles  of  black 
C.  Rinse  the  jar  with  a  little  distilled  H20,  pour  the  H20  into  an 
evaporating  dish,  add  a  few  drops  of  HCI  and  heat.  The  MgO  will 
dissolve,  leaving  the  black  particles  floating  in  the  clear  liquid. 

198.  Chemical    Properties.  —  Carbon  dioxide, 
being  the  product  of  complete  combustion,  is  incombusti- 
ble.    It  is  a  non-supporter  of  ordinary  combustion.     Its 
solution  in  water  is  often  considered  true  carbonic  acid 
(H  2C03).     The  gas  may  be  completely  absorbed  by  a  solu- 
tion of  potassium  hydrate  (KHO). 

Experiment  194  . —  Pass  a  stream  of  C02  through  lime  water. 
Notice  that  the  formation  of  CaCO3  soon  renders  the  water  turbid 
but  that,  the  current  being  continued,  the  turbidity  soon  disappears. 
When  the  water  has  thus  lost  its  milky  appearance,  boil  it.  The 
excess  of  C02  will  escape  in  bubbles  ;  the  liquid  will  become  turbid 
again  and  deposit  a  precipitate  of  CaC03. 

199.  Uses,  etc, — Carbon  dioxide  has  been  successfully 
used  for  extinguishing  fires  in  coal  mines,  even  when  the 
fires  had  raged  for  years  and  defied  all  other  attempts  at 
putting  them  out.     The  efficiency  of  the  common,  porta- 
ble "  fire  extinguishers"  depends  upon  this  same  property 
of  carbon  dioxide.     Water  charged  with  large  quantities 
of  the  gas  is  sold  under  the  meaningless  name  of  "  soda 


§201  SOME    CARBON    COMPOUNDS.  173 

water."  While  we  thus  see  that  it  is  not  poisonous  when 
taken  into  the  stomach,  it  is  injurious  when  breathed  into 
the  lungs.  When  largely  diluted  with  air,  it  has  a  narcotic 
effect  and  its  presence  to  the  extent  of  nine  or  ten  per 
cent,  of  the  atmosphere  is  sufficient  to  cause  suffocation 
and  death.  When  we  remember  that  the  processes  of 
respiration  and  combustion  (e.g.,  the  combustion  of  illumi- 
nants)  are  robbing  the  atmosphere  of  occupied  rooms  of 
the  invigorating  oxygen  and  yielding  immense  quantities  of 
injurious  carbon  dioxide,  we  see  that  it  is  not  easy  to  over- 
estimate the  importance  of  systematic  school  and  house- 
hold ventilation,  even  ignoring  the  many  other  causes 
for  its  necessity.  While  thus  destructive  of  animal  life  it 
is  essential  to  vegetable  existence. 

Water  containing  carbon  dioxide  in  solution  is  capable 
of  dissolving  calcium  carbonate  and  other  substances  that 
are  insoluble  in  pure  water.  In  this  way,  many  rocks  are 
disintegrated,  stalagmites  and  stalactites  formed,  or  the 
soil  fitted  for  the  needs  of  plants.  It  is  also  used  in  "cor- 
roding "  lead  for  use  as  a  paint  (lead  carbonate)  and  in  the 
preparation  of  sodium  and  other  carbonates. 

200.  Test. — The  precipitation  of  calcium  carbonate 
when   carbon  dioxide  is  passed   through  lime  water  or 
shaken  with  it,  is  the  most  common  test  for  the  gas.     Its 
power  of  extinguishing  flame  is  often  a  convenient  but 
not  a  definite  means  of  detecting  its  presence. 

201.  Carbon   Bisulphide.  —  Carbon  disulphide 
(CS2)  is  prepared  synthetically  on  a  large  scale  by  passing 
sulphur  vapor  over  glowing  coke  or  charcoal. 

C2  +  2S2  =  2CS2. 


174  SOME    CARBON    COMPOUNDS.  §  202 

Caution. — Li  performing  experiments  with  CS.,,  see  that  there  is  no 
flame  near. 

Experiment  195. — Put  a  few  drops  of  CS3  into  each  of  four  small 
test  tubes.  Into  the  first  tube  put  a  little  powdered  S ;  into  the 
second,  a  few  crystals  of  I  ;  into  the  third,  a  very  small  piece  of  P  • 
into  the  fourth,  a  little  H20.  Notice  the  solubility  of  the  S,  I  and  P 
in  CS2  and  the  insolubility  of  CS2  in  H20. 

Experiment  196. — Wet  a  block  of  wood  and  place  a  watch  crystal 
upon  it.  A  film  of  H20  may  be  seen  under  the  central  part  of  the 
glass.  Half  fill  the  crystal  with  CS2  and  rapidly  evaporate  it  by 
blowing  over  its  surface  a  stream  of  air  from  the  luugs  or  a  small 
bellows.  So  much  heat  is  rendered  latent  in  the  vaporization  that 
the  watch  crystal  is  firmly  frozen  to  the  wooden  block.  (Ph.,  g§ 
526,  527.) 

Experiment  197.— Into  a  glass  cylinder,  pour  a  few  drops  of  CS2. 
In  a  few  moments  the  cylinder  will  be  filled  with 
the  heavy  vapor  of  CS2.  Thrust  the  end  of  a  glass 
rod,  heated  not  quite  to  redness,  into  the  cylinder. 
The  vapor  will  be  ignited.  See  Exp.  82. 
302  +  CS2  =  C02  +  2S02. 

2O2.    Properties. — Ordinary   carbon 
disulphide  is  a  liquid  of  light  yellow  color 
and  offensive  odor.     Its  vapor  is  injurious 
to  animal  and  vegetable  life  and  exceedingly 
inflammable.    As  it  is  heavier  than  water 
and  insoluble  therein,  it  is  easily  preserved 
under  water.     It  is  diathermanons,  has  a 
highly  refractive  effect    upon  light    (Ph., 
§§  552,    553,  613),    evaporates    rapidly  at 
ordinary  temperatures  and  boils  at   about 
FIG.  86.       46^0.,  yielding  a  heavy  vapor  that  ignites 
at  about  150°  C.,  and  that  forms  an  explosive  mixture  with 
air. 

(a.)  When  pure,  CS2  is  colorless  and  has  an  agreeable  odor  re- 
sembling that  of  chloroform. 

2O3.  Uses. — Carbon  disulphide  is  used  as  a  solvent 
for  phosphorus^  iodine,  sulphur,  and  many  resins  and  oils. 


§  205  SOME    CARBON    COMPOUNDS.  175 

It  is  used  largely  in  the  extraction  of  fats  and  oils  and  in 
the  cold  process  of  vulcanizing  caoutchouc. 

204,  Cyanogen.  —  This  compound  of  carbon  and 
nitrogen  (CN  or  Cy)  is  a  univalent  radical  (-C=N).     It  was 
the  first  compound  radical  isolated.     It  will  be  noticed 
that  it  has  two  symbols,  the  first  of  which  indicates  its 
chemical  composition.     It  is  generally  prepared  by  heating 
the  cyanide  of  gold,  silver  or  mercury,  and  collecting  over 
mercury. 

Hg"Cy2  =  Hg  +  Cy2    or    Hg"(CN)2  =  Hg  +  (CN)2. 

Cyanogen  is  a  colorless,  poisonous,  inflammable  gas.  It 
acts  like  a  monad  element,  forming  compounds  corre- 
sponding to  the  chlorides,  e.  g. : — 

Free  chlorine CI2    Free  cyanogen Cy3  or  C2N2 

Potassium  chloride KCI    Potassium  cyanide.. . .  KCy  or  KCN 

Hydrochloric  acid HCI  |  Hydrocyanic  acid. . .  HCy  or  HCN 

Some  of  the  cyanides  will  be  subsequently  noticed. 

205.  Hydrocyanic  Acid.— Hydrocyanic  acid  (cyan- 
hydric  acid,  HCN  or  HCy)  may  be  prepared  by  passing  hy- 
drogen sulphide  over  mercury  cyanide  heated  to  about 
3G°C.      HgCy2  +  H2S  =  2HCy  +  HgS.     It  is  a  volatile, 
inflammable,    intensely  poisonous    liquid.      Its  aqueous 
solution  is  well  known  as  prussic  acid. 

Caution. — Potassium  cyanide  is  intensely  poisonous,  not  only  when 
taken  internally,  but  also  when  brought  into  contact  with  an  abrasion 
of  the  skin,  a  cut  or  scratch. 

Experiment  198.—  Place  a  small  quantity  of  powdered  potassium 
cyanide  in  a  test  tube  and  add  a  few  drops  of  strong  H2S04.  The 
escaping  HCy  produces  effervescence  and  may  be  detected  by  its 
peculiar  odor,  like  that  of  bitter  almonds.  The  reaction  is  similar 
to  that  between  NaCI  and  H2S04  in  the  preparation  of  HCI. 


v>  '  •/• 

176  SOME    CARBON    COMPOUNDS.  §  205 

EXERCISES. 

1.  In  Exp.   181,  the  potassium  ferrocyanide  (K4FeC6N6)  contains 
3H20  as  "  water  of  crystallization,"     Additional  H30  is  furnished  by 
the  commercial  H  2  SO  4.     Among  the  products  are  to  be  found  potas- 
sium sulphate  (K2S04),  iron  sulphate  (FeS04)  and  ammonium  sul- 
phate  [lNH4)._,S04].     Write  the  reaction  for  that  experiment. 

2.  Write  the  graphic  symbols  and  the  names  of  H.,COo,  Na2C03 
and  HNaC03. 

3.  Write  an  equation  showing  what  becomes  of  the  CO.,  removed 
from  the  CO  in  Exp.  182.  ^~ 

4.  Write  the  reaction  for  Exp.  182.  /b  --;  CkJ+n  }$  fa^&C    ^Wj 

5.  When  free  cyanogen  is  mixed  with  an  excess  of  0  and  an  elec- 
tric spark  passed  through  the  mixture,  an  explosion  occurs.     On 
cooling,  the  residual  gases,  one  of  which  is  N,  have  the  same  volume 
as  the  original  mixed  gases.     Write  the  reaction.  #  yi 

6.  What  is  the  weight  of  a  liter  of  cyanogen  gas  ?  t    \,\^(/ 

7.  How  would  you  prove  the  solubility  of  HCI,  NH3  and  C02?    ' 

8.  (a.)  What  weight  of  C0g  would  be  produced  by  burning  5  g. 
rofC?    (6.)  What  volume?  ;<  '>&  . 


9.  (a.)  What  weight  of  C02  may  be  obtained  from  100  g.  of  CaC03 
by  the  action  of  HCI  ?    (6.)  What  volume?  -I  l 


10.  What  is  the  weight  of  10  I.  of  CO3  ?yf  ftf' 

11.  (a.)  If  20  cu.  cm.  of  CO  and  10  cu.  cm.'  of  6  be  mixed  in  an 
eudiometer  and  an  electric  spark  passed  through,  what  will  be  the 
name  and  volum3  of  the  product?    (6.)  Write  the  reaction,     (c.)  If 
this  product  be  agitated  with  a  solution  of  KHO,  what  will  be  the 
effect  upon  the  gaseous  volume  ? 

12.  Write  the  empirical  symbols  for  nitrosyl  chloride  and  sulphuryl 
chloride.  f/&  &l  f$0}&1*^ 

13.  Give  the  laboratory  mode  of  liberating  COo,  with  the  reaction,  9?'' 
and  the  per  centage  composition  of  the  source  of  the  C02. 

14.  (a).  How  many  liters  of  C02  can,  be  obtained  from  200^.  of 
CaCO{?    (&.)  Howmanv,  if  the  carbonate  contains  3  percent,  of 

ilica?    /;;    :  fjUH 

-JJ^JSS1.^.  If  sulphuryl  chloride  be  poured  into  H2O,  we  have  the  follow- 
ing reaction:  SO2CI2  +  2H.20  =  H2SO4  +  2HCI.  How  milch  dry 
HCI  may  be  thus  prepared  from  135  g.  of  S02CI2  ?  J  '$ 

16.  Describe  a  method  of  preparing  0,  and  express,  by  symbols, 
the  changes  that  take  p^ce.  X/ft^J*  3- 

17.  How  is  HNO3  prepared?    Express,  by  symbols,  the  changes. 

18.  Explain  and  illustrate  what  you  understand  by  quantivalence. 

19.  Give  the  specific  gravity  of  C02,  NH3,  HCI,  and  H2,  with  the 
principle  by  which  it  is  easily  determined. 


§207 


SOME   HYDROCARBONS. 


177 


SOME     HYDROCARBONS. 

206.  Hydrocarbons. — The  compounds  of  hydrogen 
and  carbon  are  called  hydrocarbons.     They  are  so  very 
numerous  that  any  attempt  at  even  naming  them  would 
carry  us  beyond  the  proper  limits  of  an  elementary  text 
book.     They  are  capable  of  classification  into  series,  each 
one  differing  but  little  in  composition  and  properties  from 
its  neighbors  in  its  series.     (See  §  220.) 

207.  Marsh  Gas. — Marsh  gas  (methyl  hydride,  hy- 
drogen monocarbide,  methane,  CH4)  occurs  free  in  nature, 
being  a.  product  of  the  decay 

of  vegetable  matter  confined 
under  water.  In  warm  sum- 
mer weather,  bubbles  often 
rise  to  the  surface  of  stagnant 
pools.  If  the  vegetable  mat- 
ter at  the  bottom  of  the  pond 
be  stirred,  the  gas  bubbles  will 
rise  rapidly.  The  gas  may  be 
collected  by  filling  a  bottle  with  water,  tying  a  funnel  to 
its  mouth,  as  shown  in  Fig.  87,  and  inverting  it  over  the 
ascending  bubbles.  Of  this  gas,  about  75  per  cent,  is 
marsh  gas;  the  rest  is  chiefly  carbon  dioxide  with  some 
nitrogen.  The  carbon  dioxide  may  be  removed  by  agita- 
ting the  mixed  gases  with  lime-water.  Marsh  gas  also 
escapes  from  seams  in  some  coal  mines  and  forms  the 
dreaded  "  fire  damp "  of  the  miner.  It  also  escapes  in 


FIG.  87. 


178  SOME    HYDROCARBONS.  §207 

large  quantities  from  "  gas  wells  "  in  petroleum  producing 
regions.  It  is  the  first  of  a  homologous  hydrocarbon  series 
known  as  "  The  Marsh  Gas  Series." 

Experiment  190. — Into  a  gas  pipe  retort  (App.  22)  15  or  20  cm.  long, 
put  an  intimate  mixture  of  3g.  sodium  ac-tate,  3  g.  sodium  hydrate, 
(caustic  soda,  NaHO)  and  6  g,  quicklime.  Place  the  retort  in  a 
stove,  heat  to  redness  and  collect  the  gas  over  H2O. 

Experiment  200.—  The  levity  and  inflammability  of  CH4  maybe 
shown  as  in  the  case  of  H,  by  introduc. 
ing  a  lighted  taper  into  an  inverted  jar 
of  it.  The  gas  will  burn  at  the  mouth 
of  the  jar,  and  the  candle  flame,  as  it 
passes  up  into  it,  will  be  extinguished. 


Experiment  201.—  Fill  a  tall  bottle  of 
at  least  one  liter  capacity  with  warm 
H30,  invert  it  over  tha  water  pan,  and 
pass  CH4  into  it,  until  a  little  more  than 
one-third  of  the  H20  is  displaced  ;  cover 
the  bottle  with  a  towel,  to  exclude  the 
light,  and  then  fill  the  rest  of  the  bot- 
IG'  88'  tie  with  Cl.  Cork  the  bottle  tightly,  and 

shake  it  vigorously,  to  mix  the  gases  together,  keeping  the  bot- 
tle covered  with  the  towel.  Then  open  the  bottle  and  apply  a 
flame  to  the  mixture.  HCI  will  be  produced,  and  the  sides  aud 
mouth  of  the  bottle  become  coated  with  solid  C  in  the  form  of  lamp- 
black. Test  for  HCI  with  moistened  blue  litmus  paper  and  with  a 
rod  wet  with  NH^HO. 

2O8.  Properties. — Marsh  gas  is  a  colorless,  odorless, 
tasteless  gas,  but  slightly  soluble  in  water.  With  the  ex- 
ception of  hydrogen,  it  is  the  lightest  known  substance. 
It  is  combustible,  burning  with  a  feebly  luminous,  bluish- 
fellow  flame.  Its  calorific  power  is  very  great  (Ph.,  §  569). 
It  forms  an  explosive  mixture  with  air  or  oxygen  and  has 
been  the  cause  of  many  terribly  fatal  explosions  in  ill- 
ventilated  coal  mines.  When  decomposed  by  electric 
sparks,  it  yields  twice  its  volume  of  hydrogen.  It  may  be 


§  210  SOME    HYDROCAEBOXS.  179 

considered  a  hydride  of  the  univalent  compound  radical, 
methyl  (CH3). 

(a.)  A  mixture  of  CH  4  with  twice  its  volume  of  0  is  more  violently 
explosive  than  a  similar  mixture  of  H  and  0. 

2O9.  Chloroform.—  When  chlorine  is  allowed  to  act 
on  methyl  hydride,  the  hydrogen  of  the  latter  is  gradually 
replaced,  forming  successively  CH3CI,  CH2Ci2,  CHC13  and 
CCI4.  Chloroform  (CHCI3)  may  be  considered  as  marsh 
gas  in  which  three  hydrogen  atoms  have  been  replaced  by 
three  chlorine  atoms!  It  is  a  colorless,  volatile  liquid, 
much  used  as  an  anaesthetic  in  surgical  operations.  It  is 
manufactured  by  distilling  dilute  alcohol  with  chloride  of 
lime. 

Marsh  Gas.  Chloroform.  > 

H-t-H  Cl-t-CI 


21O.  Alcohol.  —  When  the  juices  of  plants  and  fruits 
that  contain  sugar/e.0.,  the  juice  of  the  grape  or  apple, 
stand  for  some  time  in  a  warm  place,  they  begin  to  fer- 
ment. The  fermentation  may  be  aided  by  the  action  of 
yeast.  The  fermented  liquid  has  lost  the  sweet  taste  of  the 
sugar  because  the  sugar  (C6H,206)  has  been  decomposed 
into  carbon  dioxide  and  alcohol  (C2H60).  See  Exp.  187. 
The  preparation  of  alcohol  is  illustrated  by  Exp.  202. 

(a.)  The  chief  peculiarity  of  the  hydrocarbons  arises  from  the  facil- 
ity with  which  the  C  atoms  unite  themselves  one  to  another  and 
thus  constitute  the  framework  of  the  various  molecules.  For  exam- 

V 

pie,  we  have  the  methane  molecule,  H-C-H.     By  replacing  one  atom 

HI 


180  SOME    HYDROCARBONS.  §  210 


of  H  with  the  univalent  radical  methyl  (CH3),  we  have  H-C-C-H, 

H  H 

or  ethane  (ethyl  hydride).     By  substituting  the  univalent  radical, 

H  H 

HO,  for  one  atom  of  the  H  in  ethane,  we  have  (HO)-C-C-H,  or  ordinary 

HH 

alcohol  (ethyl  hydrate).    By  successive  substitutions  of  (CH3yfor  H, 

H  H  H  H 

we  may  pass  from  CH4  to  C3H6,  C3H8,  C4Hio  or  H-C-C-C-C-H,  etc. 

HH   H^ 

Experiment  202.  —  Pour  half  of  the  fermented  liquid  of  Exp.  187 
into  a  flask,  F,  placed  on  the  ring  of  a  retort  stand.  Connect  Fwith 
an  empty  flask  or  bottle,  b,  having  a  capacity  of  about  100  cu.  cm., 
and  placed  in  a  water  bath.  Connect  6  with  a  flask  or  bottle,  c,  im- 


FIG.  89. 

mersed  in  cold  H20,  as  shown  in  Fig.  89.  Boil  the  liquid  in  F;  the 
vapors  of  C3H6O  and  of  H20  pass  into  b,  the  temperature  of  which 
is  a  little  below  the  boiling  point  of  H2O  (100~C.)  because  its  water 
bath  is  kept  barely  boiling  [Ph.,  §§  502  (2),  513.]  Here,  most  of  the 
steam  is  condensed  while  the  vapor  of  C2HC0  passes  on  to  c,  and  is 
there  condensed.  The  distillate  condensed  in  c  is  dilute  alcohol.  If 
it  is  not  strong  enough  to  burn  when  a  flame  is  brought  into  contact 
with  it,  it  may  be  distilled  again,  or  a  second  bottle  and  water  bath, 
6',  may  be  interposed  between  b  and  c.  The  experiment  should  not 
be  continued  after  a  quarter  of  the  liquid  in  F  has  been  vaporized. 


§213 


SOME    HYDROCARBONS. 


181 


Instead  of  condensing  the  C2H60  in  the  flask,  c,  the  Liebig  con- 

denser (Ph.,  §  512,  a.},  shown  in 

Fig.  90,  may  be  used.   Some  H  2O 

will  remain  in  the  C2H60  even 

after  re-distillation.     This  may 

be  removed  by  quicklime. 

211.  Properties.—  Al- 

cohol is  a  colorless,  volatile, 

inflammable  liquid.  Its  spe- 

cific gravity  is  0.8  and  its 

boiling  point  78°C.     It  ab- 

sorbs moisture  from  the  at- 

mosphere  and  is  capable  of 

mixing  with   water  in  all 

proportions.     Alcohol  that  contains  no  water  is  called  ab- 

solute alcohol.    Alcohol  that  is  "  90  per  cent,  proof"  is  con- 

sidered to  be  of  good  quality.     As  marsh  gas  is  considered 

to  be  a  hydride  of  methyl,  so  ordinary-  alcohol  is  consid- 

ered to  be  a  hydrate  (§  167)  of  the  univalent  compound 

radical,  ethyl  (C2H5). 

212.  Uses.  —  Alcohol  is  largely  used  in  the  chemical 
laboratory,  in  pharmacy  and  in  the  arts.     It  affords  a 
smokeless  fuel  and  is  an  indispensable  solvent  for  many 
substances  (such  as  resins  and  oils)  that  are  insoluble  in 
water.    It  is  the  fundamental  principle  of  all  fermented 
and  distilled  liquors. 

213.  Ether.—  Ether  [«  sulphuric  ether,"  ethyl  ether, 
ethyl  oxide,  (C2H5)20]  is  prepared  by  distilling  a  mixture 
of  strong  sulphuric  acid  and  alcohol.    The  distillate,  which 
is  a  mixture  of  ether  and  water,  is  condensed  in  a  cold  re- 
ceiver and  separates  into  two  layers,  water  below  and  ether 
above.      The  ether  is  drawn  off  and  wholly  freed  from 
water  by  standing  over  quicklime  and  redistillation. 


182  SOME    HYDROCARBONS.  §  213 

(a.)  The  chemical  reaction  may  be  represented  as  follows  : 
Alcohol.  Hydrogen  Ethyl  Sulphate 

(C2H5)HO  +  H,S04  =  H20  +  H(C2H-)S04. 

H(C2H5)S04  +  (CaH5)HO  =  (C8H8)80  +  H8S04. 

It  will  be  noticed  that  the  full  amount  of  H2S04  engaged  remains 
at  the  end  of  the  reaction.  C3H60  is  supplied  in  an  uninterrupted 
stream,  and  thus  the  distillation  goes  on  continuously. 

Caution.  —  Owing  to  the  danger  arising  from  the  extreme  volatility 
and  inflammability  of  (C2H5)2O,  the  pupil  should  deal  with  only 
minute  quantities  of  this  compound. 

Experiment  203.—  Put  10  or  12  drops  of  C2H6O  and  an  equal 
quantity  of  H2S04  into  a  test  tube  and  heat  gently.  The  peculiar 
odor  of  (C2H5)20  may  be  recognized. 

Experiment  26  1£.  —  Pour  a  small  quantity  of  (C2H5)3O  into  the 
palm  of  the  hand  and  notice  its  rapid  evaporation  and  absorption  of 
sensible  heat  (Ph.,  §  517). 

Experiment  205.  —  Put  a  few  drops  of  (C2H5)20  into  a  tumbler, 
cover  loosely  and,  after  the  lapse  of  a  minute,  bring  a  flame  to  the 
edge  of  the  tumbler.  .The  heavy  vapor  of  (C2H5)30  will  ignite  with 
a  sudden  flash. 

214.  Properties.  —  Ether  is  a  colorless,  volatile,,  in- 
flammable liquid,  having  a  specific  gravity  of  0.72.  It  is 
almost  insoluble  in  water  and  has  a  strong  and  peculiar 
odor.  It  is  largely  used  as  an  anaesthetic  (§§  80,  2C9) 
in  surgical  operations.  Its  common  name,  "sulphuric 
ether,"  is  a  misnomer  as  ether  contains  no  sulphur.  Ether 
may  be  considered  as  ethyl  oxide. 

Note.  —  The  relations  of  C2HC0  and  (C2H5)20  to  each  other  and 
to  their  compound  radical,  ethyl,  may  be  made  more  evident  by  the 
following  typical  symbols  (§  96)  : 

Water  Type.  Alcohol.  Ether. 


215.  Acetic  Acid.—  If  the  half  of  the  fermented 
liquid  of  Exp.  187  remaining  after  Exp.  202  be  tasted. 


§  2l6  SOME    HYDROCARBONS.  183 

after  standing  for  a  few  days,  it  will  be  found  to  be  sour. 
If  allowed  to  stand  long  enough,  it  will  be  changed  to  vin- 
egar. By  a  process  of  oxidation,  the  alcohol  is  changed 
to  acetic  acid  ("  pyroligneous  acid,"  C2H402,)  and  water. 
Vinegar  is  a  dilute  solution  of  acetic  acid  with  coloring 
matter  and  other  impurities  from  the  juice  of  the  fruit 
from  which  it  is  generally  made. 

(a.)  If  two  atoms  of  H  in  the  compound  radical  C2H.  be  replaced 
by  0  we  shall  have  the  oxygenated  radical  C3HaO,  called  acetyl. 
This  radical  has  not  yet  been  isolated.  It  is,  consequently,  a 
"  hypothetical,  oxygenated,  compound  radical."  Acetyl  hydride 
(C2H,0,H),  a  volatile,  unstable  and  easily  oxidizable  compound, 
is  called  aldehyde;  acetyl  hydrate  (C2H30,HO)  is  called  acetic 
acid.  This  acid  is  monobasic. 

(b.)  The  conversion  of  C2H60  to  C2H403  is  represented  by  the  fol- 
lowing equations : 

Alcohol.  Aldehyde. 

(C2H5)HO  +  0  =  H30  +  (C2H30)H. 

Acetic  add. 
(C2H30)H  +  0  =  (C2H30)HO  =  C8H402. 

(c.)  Pure  C2H402  is  prepared  by  distilling  a  mixture  of  H2S04 
and  some  acetate,  such  as  sodium  acetate.  Lead  acetate  is  commonly 
called  by  the  dangerous  name,  "sugar  of  lead;"  copper  acetate  is 
called  "  verdigris." 

(d.)  We  have  already  noticed  the  relation  between  ethyl,  alcohol 
and  ether.  The  relations  of  acetic  acid  to  these  may  be  shown  as 
follows : 

Ethyl  (C2H5),  when  oxygenated,  becomes  acetyl  (C2H30). 
Acetyl  (C2H30)  with  hydroxyl  becomes  acetic  acid  or  acetyl  hy- 
drate (C2H402). 

216.  Isomerism. — Acetic  acid  and  methyl  formate 
are  two  distinct  substances,  having  different  properties,  but 
represented  by  the  same  molecular  symbol,  C2H402.  Dif- 
ferent substances  having  the  same  percentage  com- 
position are  said  to1}&  isomeric ;  the  substances  are 


184  SOME    HYDROCARBONS.  §  2l6 

called  isomers;  the  peculiar  phenomenon  is  called 
isomerism.  Isomers  that  have  the  same  molecular  sym- 
bol, like  acetic  acid  and  methyl  formate,  are  said  to  be 
metameric.  Isomers  that  have  different  molecular  sym- 
bols are  said  to  be  polymeric.  Acetylene  (C2H2)  and 
benzene  (C6H6)  are  polymers. 

(a.)  There  are  at  least  seven  distinct  substances  having  the  symbol 
Ci0H6CI2,  differing  from  each  other  in  solubility,  fusibility  and 
chemical  behavior.  We  can  only  imagine  that  the  difference  be- 
tween metameric  substances  is  due  to  a  difference  in  -the  arrange- 
ment of  the  atoms  in  the  molecule. 

(&.)  Isomeric  substances  bring  clearly  to  view  the  value  of  rational 
symbols  (§  94).  Formic  acid  (CH203)  is  a  hydrate  of  the  univalent 

radical,   formyl  :  CH^  j  0.     Replacing  the  H  in  this  typical  sym- 


bol for  formic  acid  by  methyl  (CH3)',  we  have  ^°  j-  0  as  the 
typical  symbol  for  methyl  formate.  Acetic  acid  is  a  hydrate  of  the 
univalent  radical,  acetyl  :  CaH3^  ?  Q  While,  therefore,  the  empiri- 
cal symbol,C2H4O2  affords  no  means  of  distinguishing  between  acetic 
acid  and  methyl  formate,  the  typical  symbols,0^  3°  j-  0  and  ^°  j-  0 

represent  clearly,  to  eye  and  mind,  two  distinct  substances.  Simi- 
larly, C2H60  represents  common  alcohol  or  methyl  ether.  The 

C  H    ) 
former  is  ethvl  hydrate,      2  u  !-  0  ;    the  latter  is  methyl    oxide, 

iS:l°- 

(c.)  Isomerism  is  a  peculiarity  of  the  hydrocarbons.  The  several 
members  of  the  olefiant  gas  series  (§  220)  are  polymers. 

217.  Olefiant  Gas.  —  Olefiant  gas  (ethene,  ethylene, 
hydrogen  dicarbide,  C2H4)  is  prepared  by  removing  the 
elements  of  water  from  alcohol.  It  is  the  first  of  a  homol- 
ogous hydrocarbon  series,  known  as  "  The  Olefiant  Gas 
Series." 

Experiment  206.  —  In  a  large  beaker  glass,  mix  120  cu.  cm.  of 
H2S04  and  30  cu.  cm.  of  C2H60,  with  caution  and  constant  stirring. 
Half  fill  a  liter  flask  with  coarse  sand  and  pour  the  mixed  liquids 
upon  the  sand.  Close  the  flask  with  cork  and  delivery  tube,  and 


§  219 


SOME   HTDROCARBOXS. 


185 


heat  it  gently  upon  the  sand  bath.  The  gas  will  be  delivered  mixed 
with  aeriform  C,H6O,  (C2H5)20,  C02  and  S02,  and  maybe  collected 
over  water.  If  pure  C3H4  be  desired,  two  wash  bottles,*  one  contain- 
ing strong  Ho  SO  4  and  the  other,  a  solution  of  NaHO  may  be  inter- 
posed between  the  flask  and  the  water  bath.  The  purpose  of  using 
the  sand  is  to  lessen  the  frothing  in  the  flask. 

C3H60-H20  =  C2H4. 

Experiment  207.— Apply  a  flame  to  the  mouth  of  a  bottle  of  C,H  t 
and  force  out  the  gas  by  pour- 
ing in  H20.    The  C2H4  burns 
with  a  brilliant  white  flame. 
C2H4  +  302  =  2C02  +  2H20. 

Experiment  208.— Fill  ascda 
water  bottle  with  one  volume 
of  CSH4  and  three  volumes  of 
0.  Wrap  a  towel  about  the 
bottle  and  apply  a  flame  to  the 
mouth  of  the  bottle.  A  vio- 
lent explosion  will  take  place. 

Experiment  209.— Half  fill  a 
liter  flask  over  the. water  bath 


under  H20,  half  a  liter  of  Cl 


FIG.  91. 


into  the  flask,  and  place  a  small  cup  under  the  mouth  of  the  flask. 
The  1,000  cu.  cm.  of  mixed  gases  will  rapidly  decrease  in  volume, 
H20  will  rise  in  the  flask  and  oily  drops  will  be  formed  and  fall 
through  the  H20  into  the  cup  beneath.  There  has  been  a  direct 
synthesis  of  the  two  gases  to  form  ethylene  chloride,  ("  Dutch  liquid," 
or  u  oil  of  the  Dutch  chemists,"  C2H4CI2).  Hence  the  name,  "  olefi- 
ant  gas."  By  agitating  the  C2H4C12  with  a  solution  of  sodium  car- 
bonate, the  former  may  be  purified  and  its  agreeable  odor  obtained. 
(See  Note  following  Exp.  94.) 

218.  Properties.  —  Olefiant  gas  is  colorless,  com- 
bustible and  irrespirable.  It  is  slightly  soluble  in  water, 
and  forms  an  explosive  mixture  with  three  times  its  vol- 
ume of  oxygen.  It  may  be  decomposed  by  electric  sparks, 
giving  twice  its  volume  of  hydrogen. 

319.   Acetylene.  —  Acetylene   (ethine,  C2H2)  is  a 


186  SOME    HYDROCARBONS.  §  2IQ 

transparent,  colorless  gas,  that  burns  with  a  strongly  lu- 
minous, smoky  flame.  It  acts  as  a  poison  when  it  comes 
into  contact  with  the  blood.  It  may  be  formed  by  direct 
synthesis  of  its  constituents  at  very  high  temperatures.  It 
is  one  of  the  ingredients  of  illuminating  gas. 

(a.)  Carbon  electrodes  may  be  fitted  to  pass  through  apertures  in  a 
globular  glass  flask,  through  which  a  slow  current  of  pure  H  is  flow- 
ing. By  passing  a  powerful  electric  current  through  the  carbons  and 
then  separating  them,  the  electric  arc  is  produced  in  an  atmosphere 
of  H.  This  process  results  in  the  synthesis  of  C2H2. 

22O.  Homologous  Series.— Methane,  ethene  and 
ethine  represent  each  a  series  of  hydrocarbons.  In  each 
series,  the  addition  of  CH2  to  the  symbol  of  one  member, 
gives  the  symbol  of  the  next  member.  Hydrocarbons 
that  differ  thus  from  one  another  are  said  to  belong 
to  homologous  series. 

(a.)  Each  series  has  its  general  formula  or  symbol  : 

Series.            General  Formula.  Symbols  of  Members. 

Marsh  gas CnH2n  +  9  CH4  ;  C3H6  ;  C8H8  ;  C4H10;  C5H12 

Olefiantgas CnH2n  C2H4  ;  C3H6 ;  C4H8  ;    C5H10 

Acetylene CnH2n-2 


EXERCISES. 

1.  (a.}  What  is  the  specific  gravity  of  marsh  gas,  on  the  hydrogen 
standard  ?    (b.)  On  the  air  standard  ?    (c.)  What  will  a  molecule  of 
it  weigh  ?    (d.)  What  will  a  liter  of  it  weigh  ? 

2.  (a.)  What  are  the  products  of  the  combustion  of  methyl  hy-^^ 
dride  ?    (6.)  When  a  liter  of  it  is  burned,  what  is  the  weight  of  th£-^«y 
dioxide  produced  ?     (c.)  Of  the  monoxide  produced  ?/t  y  .  w  y 

3.  (a.)  What  volume  of  0  is  necessary  to  the  complete  combustion 
of  a  liter  of  CH4  ?    (&.)  What  weight  of  0  ? 

4.  Find  the  percentage  composition  of  alcohol. 

5.  (a.}  What  is  the  weight  of  a  molecule  of  ethyl  oxide?    (&.)  Of 
a  liter  of  ether  vapor  ?    (c.)  Of  a  liter  of  liquid  (C2H5)20  ? 


§  220  SOME    HYDROCARBONS.  187 

6.  (a.)  What  volume  of  H  may  be  obtained  by  the  decomposition 
of  500  en.  cm.  of  olefiant  gas  ?    (&.)  By  the  decomposition  of  10.5  criths 
of  ethylene? 

7.  Which  is  the  heavier,  C2H4  or  N2  ? 

8.  (a.)  Give  a  short  statement  of  the  process  for  making-  sulphuric 
acid.    (&.)  Which  is  the  most  interesting  action  in  the  process?    (c.) 
What  is  the  specific  gravity  of  the  acid  and  how  is  this  specific  grav- 
ity secured  ? 

9.  When  a  mixture  of  H  and  CO   is  exposed  to  the  action  of  a 
',  '/2.   Aeries  of  electric  sparks  the  following  reaction  takes  place  : 

3H2  +  CO  =  CH4  +  H80. 

?f6j-  -  What  volume  of  methane  can  thus  be  produced  from  12  544  g.  of 
carbon  monoxide  ? 

10.  (a.)  Show  that  the  specific  gravity  of  a  compound  gas  is  one 
half  its  combining  weight.     (&.)  How  many  atoms  are  there  in  a 
molecule  of  P? 

11.  The  composition  of  a  compound  gas  is  85 f  per  cent,  of  C  and 
14|  of  H  ;  its  density  is  14  ;  what  is  is  symbol  ?  £^  - 

12.  Account  for  the  fact  that  23 #.  of  C2H  f)0  will,  without  any  addi- 
tion of  material  by  the  manufacturer,  yield  about  30  g.  of  C2H402. 

13.  Find  the  symbol  of  a  substance  whose  vapor  density  is  23  and 
whose  analysis  shows  the  following  percentage  composition  : 

C,52.2;  H,  13;  0,  34.8.       ^>  ' 

14.  Write  the  empirical  and  graphic  symbols  for  ethyl.  H  ' 

15.  What  word  more  fully  descriptive  than  isomeric  may  be 
plied  to  substances  that  have  the  same  percentage  composition  and 
molecular  weight  ? 

16.  Symbolize  the  acetates  of  Na',  K',  Ca"  and  (NH4)'. 


188 


ILLUMINATING     GAS. 


§221 


ILLUMINATING     GAS. 

Experiment  210.  —  Into  a  gas  pipe  retnrt,  put  some  fragments  of 
bituminous  (soft)  coal.  To  the  delivery  tube,  attach  a  piece  of  glass 
tubing  drawn  out  to  a  jet.  Place  the  retort  in  a  hot  fire  and,  as  the 
illuminating  gas  is  delivered,  ignite  it  at  the  jet. 


21.  Illuminating  Gas.—  Illuminating  gas  is  pre- 

pared by  distilling  sub- 
stances consisting  in  whole 
or  in  part  of  hydrogen  and 
carbon.  For  this  purpose, 
wood,  resin,  or  petroleum  is 
sometimes  used  but,  far 
more  commonly,  a  mixture 
of  cannel  and  caking  bitu- 
minous coals  furnishes  the 
desired  products.  A  section- 
al view  of  the  apparatus  used 
is  shown  in  Fig.  93.  The 
coal  is  placed  in  Q  shaped 
FIG.  92.  retorts,  six  or  seven  feet 

long,  made  of  fire  clay.  The  charge  is  about  200  Ib.  of 
coal  to  each  retort.  The  retorts,  C,  are  arranged  in  groups 
or  "  benches  "  of  from  three  to  seven,  as  shown  in  Fig.  92. 
All  the  retorts  of  a  bench  are  heated  to  a  temperature  of 
about  1200°C.  or  2200°F.  by  a  single  coke  fire.  After 
charging  the  retorts,  their  mouths  are  quickly  closed  by 
heavy  iron  plates. 


221 


ILLUMINATING     GAS. 


189 


FIG.  93. 


190  ILLUMINATING     GAS.  §221 

(a.)  The  products  of  the  distillation,  when  cooled  to  the  ordinary 
temperature,  are  solid,  liquid  and  gaseous.  The  liquid  products  are 
volatile  at  the  high  temperature  of  the  retort. 

(&.)  The  solid  products  are  coke  and  gas  carbon.  The  coke  is  coal 
from  which  the  volatile  constituents  have  been  removed  by  intense 
heat.  It,  is  largely  used  as  a  fuel  for  domestic,  metallurgical  and 
other  purposes.  The  gas  carbon  is  an  incrustation  that  gradually 
forms  on  the  inside  of  the  retorts.  It  is  used  for  making  plates  for 
galvanic  batteries  and  "carbons"  or  "  candles  "  for  electric  lamps 
(Ph.,  §§  383,  385,  389). 

(c.)  The  liquid  portion  of  the  distillate  is  chiefly  an  aqueous  solu- 
tion of  ammonium  compounds,  certain  hydrocarbons  like  benzol 
and  toluol,  and  a  viscous  coal  tar  which  is  complex  in  its  composi- 
tion. 

(d.)  The  gases  of  the  distillate  are  very  numerous.  One  writer 
mentions  nineteen  light  producing  constituents,  including  benzol 
and  toluol  vapors,  C2H2  and  C2H4  ;  three  diluents,  viz.,  H,  CO  and 
CH4  ;  and  fourteen  impurities,  including  N,  0,  H80,  H2S,  C02,  S02 
and  CS2. 

(e.}  When  the  volatile  products  leave  the  retort,  they  pass  up 
through  the  ascension  pipes,  i,  down  the  dip  pipes  and  bubble  through 
the  seal  of  tar  and  water  already  collected  in  the  long,  horizontal 
iron  tube,  mm,  called  the  hydraulic  main.  From  this  point  forward, 
cooling  ensues,  accompanied  by  the  condensation  of  vapors  "and 
the  falling  of  the  tar  particles  mechanically  carried  along  in  the  hot 
rush  of  the  gas  from  the  retorts."  The  gas  is  loaded  with  impuri- 
ties from  which  it  must  be  freed  before  it  is  in  a  salable  condition. 

( f.)  From  the  hydraulic  main,  where  it  left  much  of  its  tar  and 
H8O,  the  gas  passes  through  the  vertical  cooling  pipes,  D,  called  the 
condensers.  Here  it  is  cooled  to  20°C.  or  25°C.  and  largely  freed 
from  its  tar,  oils  and  ammonium  compounds.  The  gas  now  assumes 
a  condition  less  thickened  and  turbid  and  more  favorable  to  chemical 
treatment.  In  large  gas  works,  there  are  many  sets  of  these  con- 
densers. In  the  Cleveland  works,  each  set  measures  840  linear  feet. 
Every  particle  of  gas  has  to  pass  the  whole  length  of  one  of  these 
sets  of  condensers. 

(g.}  In  large  works,  an  "exhauster"  is  placed  between  the  hy- 
draulic main  and  the  condensers.  By  this  means,  the  gas  is  pumped 
from  the  retorts  and  forced  through  the  condensers,  thus  reducing 
the  pressure  in  the  retorts. 


§221  ILLUMINATING    GAS.  191 

(7i.)  Chief  among  the  impurities  still  remaining,  are  ammonium 
compounds,  CO*  and  HaS.  These  ammonium  compounds  are  easily 
soluble  in  HaO.  Therefore,  the  gas  is  next  washed  in  the  tower  or 
"  scrubber,"  0.  Here  the  gas,  in  a  finely  divided  state,  rises  through 
a  shower  of  minute  particles  of  H.>0  and,  thus,  has  its  easily  soluble 
impurities  washed  out  by  the  spray.  To  prevent  the  ascent  of  the 
g.is  in  large  bubbles,  of  which  only  the  surfaces  would  come  into 
contact  with  the  H20,  the  scrubber  is  filled  with  coke,  brush,  or  lat- 
tice work  for  "  breaking  up"  both  gas  and  H30  into  minute  particles. 
This  scrubbing  also  cools  the  gas  still  more  and  removes  some  of  the 
CO 2  and  HoS.  The  tower  is  generally  three  or  four  feet  in  diameter 
and  thirty  or  forty  feet  high.  More  than  one  are  used  in  some  works. 

(i.)  The  gas  next  passes  through  the  purifiers,  M,  the  object  of 
which  is  to  remove  the  remaining  C02  and  H2S.  The  purifier  con- 
sists of  boxes  containing  trays  with  perforated  bottoms.  These  trays 
contain  the  material  which  removes  the  impurities  as  the  gas  filters 
through.  Some  works  use  slaked  lira  3  in  the  purifiers,  others  a 
mixture  of  copperas  (iron  sulphate,  FeS04,)  saw-dust  and  slaked 
lime.  At  manufacturing  establishments  where  iron  and  steel  arti- 
cles are  polished,  the  grindstone  dust  is  intimately  mixed  with 
minute  particles  of  the  metal.  This  inexpensive  mixture  of  grind- 
stone dust  and  iron  or  steel  is  used  in  the  purifiers  of  the  Cleveland 
Gas  Light  and  Coke  Co. 

(j.)  From  the  purifiers,  the  gas  is  conducted  to  the  gasholders,  Q. 
These  gas  holders  are  sometimes  sixty  feet  high  and  more  than  100 
feet  in  diameter. 

(&.)  The  gas,  as  delivered  to  the  consumer,  consists  chiefly  of  the 
three  diluents  mentioned  above,  the  CH4  constituting -about  a  third 
-  of  the  gas  sold.  These  feebly  luminous  gases,  H,  CO  and  CH4,  serve 
as  carriers  of  the  six  or  seven  per  cent,  of  more  highly  luminous  con- 
stituents, while  the  combustion  of  the  former  furnishes  much  of  the 
heat  needed  for  the  decomposition  of  the  latter  and  the  raising  of  its 
carbon  particles  to  the  temperature  of  incandescence. 

(I.)  Other  conditions  being  the  same,  and  .within  certain  limits,  the 
higher  the  temperature,  the  greater  the  quantity  of  gas  produced ; 
the  lower  the  temperature,  the  richer  the  quality.  Similarly,  the 
longer  the  time  of  the  charge,  the  greater  the  quantity;  the  shorter 
the  time,  the  richer  the  quality.  A  skillful  mixture  of  grades  of  coal 
and  regulation  of  temperature  and  time  of  charge  enables  the  gas 
engineer  to  vary  the  products  of  the  chemical  processes  in  the  retort 


192  ILLUMINATING    GAS.  §  221 

and  furnish  an  article  that  is  attractive  and  satisfactory  to  the  con- 
sumer, or  .profitable  to  the  proprietors,  or  to  compromise  between 
these  conflicting  interests. 

Experiment  211. — Heat  some  pieces  of  bituminous  coal  in  the  gas 

pipe  or  other  retort  and 
pass  the  gas  as  it  is  evolved 
through  the  apparatus 
shown  in  Fig.  94.  The 
volatile  liquid  products 
will  condense  in  the  re- 
ceiver, m,  or  "hydraulic 
main."  Thence,  the  gas 
94-  passes  through  the  first 

arm  of  the  U-tube  and  changes  the  color  of  a  moistened  strip  of  red 
litmus  paper  to  blue,  thus  showing  the  presence  of  NH,j.  In  the 
second  arm,  it  is  tested  for  H2S  (§  142).  In  the  bend  of  the  second 
tube,  is  placed  lime  water,  which  becomes  milky,  thus  showing  the 
presence  of  C02.  The  gas  is  then  collected  over  H3O.  By  lowering 
the  capped  receiver  into  the  H20  or  by  pouring  more  H20  into  the 
water  bath  and  opening  the  stop-cock,  the  gas  may  be  forced  out  and 
burned  as  it  issues. 

EXERCISES. 

1.  See  App.  1.    Read  the  following  symbols,  thus  :  N2  represents 
one  molecule  of  nitrogen  consisting  of  two  atoms  :  O,  00,  O3,  H20, 
2H20,  H2,  2P4,  CI2,  NH3,  H,S04,   FeS04,  AI2(S04)3,  ~4AI2(SOJS, 
C02,  CO. 

2.  Write  down  the  weights  represented  by  each  of  the  following 
expressions:  2Rf6;  10H20,  2CS2,  12CH4,  K2AI3(S04)4,  24H20. 

3.  Name  the  compounds  symbolized  as  follows :  CaO,  MgO,  ZnS, 
KCI,  NaBr,  AgF,  H2S,  HI,  KCN,  SSe,  PH3. 

4.  If  two  volumes  of  C2H4  and  four  of  Cl  be  mixed,  a  black  smoke 
and  HCI  are  formed.     Write  the  reaction.  <  {  ~-#// 

5.  How  much  NH;5  will  just  neutralize  10  g.  of  HCI  ? 

6.  How  many  liters  of  O  are  necessary  to  combine  (complete  com- 
bustion) with  (a.)  12  criths  of  C  ?    (&.)  2  g.  of  S  ?    (c}.  10  g.  of  C  ? 

7.  How    many    liters    of    Cl    are  necessary    to  decompose  12   I. 
of  HI? 

8.  (a.)  Distinguish  between   the  properties  of  CO  and   those  of 
C02.    (&.)  How  does  each  destroy  life?    (c.)  Give  a  test  for  each. 


§  221  ILLUMINATING    GAS.  193 

9.  Steam  and  Cl  are  passed  through  a  porcelain  tube  heated  to 
redness.     What  takes  place  ? 

10.  (a.}  What  is  meant  by  the  basicity  of  an  acid?    (6.)  By  the 
acidity  of  a  base  ?    (c.)  How  is  the  name  of  a  salt  derived  from  that 
of  an  acid  ? 

11.  Explain  the  significance  of  each  of  the  following  symbols  for 
potassium  sulphate  :  K2S04  ;  K20,S03  ; 


E8}sOa  and 


K  — 


—  v    '     A 

j/-L\y%:J4i?J  >- 

y         *    '  '"fit*  -} 


. 


194  SOME    ORGANIC    COMPOUNDS.  S  222 


SOME    ORGANIC    COMPOUNDS. 

222.  Organic  Compounds.  —  There  are  known 
to  the  chemist  many  substances  formed  by  the  subtle  pro- 
cesses of  animal  and  vegetable  life.     These  were  formerly 
supposed  to  be  incapable  of  production  in  any  other  way 
and  their  consideration  formed  a  distinct  branch  of  study 
known  as  Organic  Chemistry.     But  within  the  last  few 
years,  many  of  these  organic  compounds  have  been  pro- 
duced in  the  chemical  laboratory  from  "dead  matter." 
Each  of  these  triumphs  of  modern  chemistry  removes  a 
stone  from  the  wall  dividing  the  realms  of  organic  and  in- 
organic chemistry.     In  fact,  the  wall,  as  a  wall,  is  already 
ruined.     In  this  section,  we  shall  consider  a  few  of  the 
almost  innumerable  known  organic    compounds.      The 
molecular  structure  of  most  of  them  is  very  complicated. 

Experiment  21%. — Place  a  teaspoon ful  of  the  white  of  an  egg  in  a 
test  tube  ;  add  25  cu.  cm.  of  C2H60.  Notice  the  coagulation. 

Experiment  213. — Place  the  remainder  of  the  white  of  the  egg  in  a 
test  tube  ;  place  the  test  tube  and  a  thermometer  in  a  vessel  of  H20 ; 
heat  the  H3O  ;  notice  that  at  the  temperature  of  about  60°C.  the 
white  of  the  egg  coagulates. 

223.  Albumen. — Albumen  is  a  substance  of  very 
complicated  structure.     It  is  typical  of  a  group  of  bodies 
(histogenetic)  that  are  essential  to  the  building  up  of  the 
animal  organism,  of  which  group  the  leading  members 
are  albumen,  fibrin  and  casein.     These  differ  but  little,  if 


§  224  SOME    ORGANIC    COMPOUNDS.  195 

any.  in  their  chemical  composition,  but  widely  in  their 
properties.  They  all  exist  in  two  conditions,  the  soluble 
and  the  insoluble. 

(a.)  The  white  of  the  eggs  of  birds  is  the  most  familiar  instance  of 
albumen.  It  is  soluble  in  H20  and  coagulated  by  heat  or  C2H60. 
The  albumen  of  plants  is  found  chiefly  in  the  seed.  The  formula, 
C72H,18N18S02,,  has  been  given  for  albumen,  but  its  chemical 
composition  has  not  yet  been  satisfactorily  determined. 

(&.)  Soluble  fibrin  is  found  in  the  blood.  It  hardens  on  exposure 
to  the  air  and,  entangling  the  corpuscles  of  the  blood,  forms  the  clot. 
By  washing  the  clot  with  H30,  fibrin  is  left  as  a  white,  stringy  mass. 
Insoluble  fibrin  constitutes  muscular  fibre. 

(c.)  Casein  is  found  in  the  milk  of  animals.  It  is  not  coagulated 
by  heat  but  is  coagulable  by  rennet,  the  inner  membrane  of  the 
stomach  of  the  calf,  This  property  is  utilized  in  cheese  making. 

(d.)  All  of  the  albuminoids  "  are  amorphous,  and  may  be  kept, 
when  dry,  for  any  length  of  time,  but,  when  moist,  they  rapidly 
putrefy  and  produce  a  sickening  odor." 

Experiment  214* — Dilute  a  quantity  of  HCI  with  about  six  times 
its  volume  of.  H30.  Place  a  clean  bone  (e.g.,  the  femur  of  a  chicken) 
in  the  dilute  acid  and  allow  it  to  remain  for  three  or  four  days.  The 
mineral  part  of  the  bone  will  gradually  dissolve,  and  there  will  be 
left  a  flexible  substance  which  preserves  the  shape  of  the  bone,  and 
which,  when  dry,  has  a  translucent,  horny  appearance. 

Experiment  215. — Place  the  flexible  substance  left  from  the  last 
experiment  in  H20  and  boil  it  for  three  or  four  hours.  It  will  dis- 
solve and,  when  the  liquid  cools,  will  assume  a  jelly-like  condition. 

224:.  Gelatin.  —  The  bones  and  skins  of  animals 
contain  a  substance  called  ossein.  The  product  of 
Exp.  214  was  ossein.  When  this  substance  is  boiled 
in  water,  gelatin  is  produced.  The  product  of  Exp.  215 
was  gelatin.  Glue  is  an  inferior  quality  of  gelatin. 
Isinglass  is  nearly  pure  gelatin  ;  it  is  made  from  the 
swimming  bladder  of  the  sturgeon.  The  thin  plates  of 
mica  used  in  stoves  are  sometimes,  with  gross  impropriety, 
called  isinglass. 


196  SOME' ORGANIC  COMPOUNDS.  §225 

225.  Sugar.  —  There  are  several  varieties  of  sugar, 
among  which  the  most  important  are  sucrose,  dextrose  and 
levulose. 

226.  Sucrose. — Sucrose  (cane  sugar,  C12H220,|)  is 
found  in  the  juice  of  certain  plants,  as  sugar  cane,  sugar 
maple  and  beet  root.    In  the  manufacture  of  cane  sugar, 
the  juice  is  pressed  from  the  canes  by  passing  them  be- 
tween rollers.    The  juice  is  treated  with  milk  of  lime  and 
heated.     The  lime  neutralizes  the  acids  and  the  heat  coag- 
ulates the  albumen  in  the  juice.     The  coagulated  albu- 
men rises  and  mechanically  carries  with  it  many  of  the 
impurities,  some  of  which  have  combined  with  the  lime. 
The  scum  thus  formed  is  removed,  and  the  liquid  evapo- 
rated until  it  is  of  such  a  consistency  that  sugar  crystals 
will  form  when  the  liquid  is  cooled.     The  crystals,  when 
drained,  are  "  brown  "  or  "  muscovado  "  sugar.     The  liquid 
remaining  is  molasses. 

(a.)  Brown  sugar  is  refined  by  dissolving  it  in  H20,  filtering  the  solu- 
tion through  layers  of  animal  charcoal  and  evaporating  the  H2O  from 
the  filtrate.  When  C^H^O^  is  boiled,  part  of  it  is  changed  to  a 
mixture  of  dextrose  and  levulose,  the  proportion  thus  changed  de- 
pending upon  the  temperature  and  time  of  boiling.  To  lessen  this 
loss  of  sucrose,  the  filtered  solution  is  evaporated  in  large  "  vacuum 
pans"  from  which  the  air  and  steam  are  exhausted.  The  degree  of 
concentration  desired  is  thus  secured  more  quickly  and  at  a  lower 
temperature  (Ph.,  §§  503-505,)  thus  lessening  the  loss  and  obviating 
the  risk  of  burning.  When  the  "mother-liquor"  drains  from  the 
crystals  in  moulds,  loaf-sugar  is  left ;  when  it  is  driven  off  by  a  cen- 
trifugal machine,  granulated  sugar  is  left. 

(&.)  The  sugar  from  the  sap  of  the  sugar  maple  or  from  the  juice 
of  the  beet  root  is  identical  with  cane  sugar.  As  the  impurities  of 
maple  sugar  are  agreeable  to  the  taste  of  many  persons,  the  sugar 
is  not  refined.  Beet  sugar  is  always  refined,  as  its  impurities  are 
offensive  to  all. 

(c.)  When  sucrose  is  melted  and  allowed  to  cool  rapidly,  barley 


§  227  SOME    ORGANIC    COMPOUNDS.  197 

sugar  is  formed.     When  it  is  heated  to  about  215°C.,  H  20  is  expelled 
and  caramel  remains. 

(<?.)  Lactose  or  milk-sugar  and  maltose  are  isomeric  forms 
that  combine  with  one  molecule  of  water  of  crystallization 
(^i 2^22^11  +  H20).  The  former  exists  in  solution  in  the  milk  of 
mammals. 

227.  Dextrose  and  Levulose. — When  a  solution 
of  sucrose  is  boiled  or  subjected  to  the  action  of  yeast  or 
an  acid,  it  is  converted  into  two  isomeric  varieties  of  sugar, 
dextrose  (glucose,  grape  sugar,  starch  sugar,  C6H,206)  and 
levulose  (fruit  sugar,  C6H,206). 

Cii       /-\  L    Ul     A  PUI       A       j^PU       O 

12n22u11  +  nsu  —  v*6n12u6  +  ^6n12v6. 

This  mixture  of  dextrose  and  levulose  is  called  inverted 
sugar. 

(a.)  Dextrose  is  found  in  many  ripe  fruits.  The  "  candied  "  sugar 
of  raisins  and  other  dried  fruits  is  dextrose.  It  crystallizes  with  diffi- 
culty and  is  generally  found  in  a  sirupy  condition.  It  may  be  pre- 
pared by  boiling  starch  in  H20  acidulated  with  H2S04.  It  has  less 
sweetening  power  than  sucrose.  Large  quantities  of  glucose  are 
now  made  from  Indian  corn. 

(6.)  Levulose  is  found  with  dextrose  in  many  ripe  fruits,  in  honey, 
molasses,  etc.  It  does  not  crystallize.  It  has  less  sweetening  power 
than  sucrose. 

(c.)  Dextrose  and  levulose  may  be  fermented  (Exp.  187) ;  sucrose 
can  not  be  fermented  until  after  its  conversion  into  dextrose  and 
levulose. 

(cZ.)  If  a  beam  of  polarized  light  (Ph.,  §  667)  be  passed  through 
a  solution  of  dextrose,  the  plane  of  polarization  will  be  turned  to- 
ward the  right  (dextra  =  right  hand).  A  solution  of  sucrose  will 
turn  it  still  more.  If  the  beam  be  passed  through  a  solution  of 
levulose,  the  plane  will  be  turned  toward  the  left  (laeva  =  left« 
hand). 

(e.)  Dextrose  and  levulose  are  isomeric  with  acetic  acid,  the  mole- 
cule C6H1206  having  three  times  as  many  of  each  kind  of  atoms 
as  C2H402.  While,  therefore,  dextrose  and  levulose  are  said  to  be 
metameric,  either  one  of  them  is  polymeric  with  reference  to  C2H40S. 
See  §  216. 


198  SO  ME    ORGANIC    COMPOUNDS.  §  228 

228.  Starch. — Starch  (C6HI005)  is  a  familiar  sub- 
stance found  in  grain  (e.  g.,  wheat  and  Indian  corn),  in  the 
tuber  of  the  potato  plant  and  in  the  root,  stem  or  fruit  of 
many  other  plants.      It  is  composed  of  microscopic  gran- 
ules which  swell  and  burst,  forming  a  pasty  mass  when 
heated  in' water  nearly  to  the  boiling  point.     This  starch 
paste  forms  a  blue  color  with  iodine  (Exp.  121). 

(a.)  Tapioca,  arrow-root,  sago  and  inulin  are  varieties  of  starch. 

(&.)  When  starch  is  heated  to  about  210°C.,  it  is  changed  to  an 
isomeric  compound  called  dextrin.  Unlike  starch,  it  is  soluble  in 
H20,  forming  a  mucilaginous  liquid.  The  adhesive  compound  on 
postage  stamps  is  largely  dextrin.  When  starch  is  boiled  in  di- 
lute H2S04,  it  is  converted,  first  into  dextrin  and  then  into  glucose. 

229.  Bread  Making. — In  making  bread,  the  water 
that  is  added  to  the  flour  forms  a  dough.     The  addition  of 
emptyings  or  yeast  causes  fermentation  to  begin.    .As  the 
fermentation   proceeds,   the  carbon  dioxide  and  alcohol 
vapor  thus  produced  struggle  to  escape  through  the  tena- 
cious dough,  causing  the  latter  to  "rise."    In  the  subse- 
quent process  of  kneading,  the  half- fermented  "sponge  " 
is  evenly  distributed  through  the  loaf  and  the  large  bub- 
bles of  gas  imprisoned  in  the  dough  are  broken  up  into 
smaller  ones  and  the   bread    thus  made  finer  grained. 
After  kneading,  the  moulded  loaves  are  placed  in  the  hot 
oven.    Fermentation  is  stimulated  by  the  heat,  the  alcohol 
is  vaporized  and,   together  with  the  carbon  dioxide,  ex- 
panded.    As  these  aeriform  substances  escape  through  the 
loaf,  they  increase  its  size  and  "lightness."    If  the  pro- 
cess has  been  satisfactorily  conducted,  by  the  time  that 
fermentation  and  the  escape  of  gas  and  vapor  have  ceased, 
the  walls  of  the  bread  cells  will  be  strong  enough  to  retain 
their  form.     If  the  dough  be  allowed  to  stand  too  long 


§  230  SOME    ORGANIC    COMPOUNDS.  199 

before  baking,  the  gas  will  escape,  the  still  plastic  walls  of 
the  bread  cells  will  collapse  and  the  bread  "  fall."  If  the 
oven  be  not  hot  enough  or  if  the  dough  be  too  wet,  a 
similar  result  will  ensue  and  the  bread  will  be  "slack- 
baked."  If  the  oven  be  too  hot,  a  crust  will  form  too 
quickly,  the  gas,  being  prevented  from  escaping,  will  col- 
lect at  the  centre  and  the  loaf  be  hollow.  At  the  surface 
of  the  loaf,  a  substance  much  like  caramel  is  formed ;  this 
is  the  crust.  The  crust  also  contains  dextrin.  When  the 
crust  is  moistened  and  the  loaf  returned  to  the  oven,  the 
dissolved  dextrin  left  by  evaporation  gives  to  the  crust  a 
smooth,  shining  surface. 

23O.  Cellulose.— Cellulose  (CI8H300I5  ?)  constitutes 
the  outer  wall  of  every  vegetable  cell  and  is,  therefore, 
found  in  every  part  of  every  plant.  It  is  insoluble  in 
water  or  alcohol.  Linen  and  cotton  are  nearly  pure  cellu- 


(a.)  Cellulose  has  the  same  centesimal  composition  as  starcli 
(C6H1005)  but  is  probably  polymeric  rather  than  metameric. 

(6.)  By  treating  cellulose  with  a  mixture  of  HN03  and  H8SO4,  it 
is  changed  to  gun  cotton  (nitro- cellulose,  pyroxylin),  an  explosive  sub- 
stance  that  burns  in  air  with,  a  sudden  flash  and  no  smoke.  Gun 
cotton  may  be  considered  to  be  cellulose  with  some  of  its  H  atoms 
replaced  by  the  compound  radical  N02. 

Experiment  216.—  Dilute  25  cu.  cm.  of  H  2S04  with  10  or  12  cu.  cm. 
of  H20.  When  the  mixture  is  cold,  immerse  in  it,  for  15  or  20 
seconds,  a  piece  of  filter  paper.  Rinse  the  paper  in  H20  and  then  in 
dilute  NH4HO,  to  remove  all  traces  of  the  acid.  Finally,  rinse  the 
paper  again  in  pure  H20.  The  paper  will  have  acquired  greater 
toughness  and  rigidity  and  will  resemble  parchment  in  other  respects. 
It  has  been  changed  to  vegetable  parchment.  It  may  be  necessary  to 
repeat  the  experiment,  varying  the  time  of  immersion,  to  get  good 
results. 


200  SOME    ORGANIC    COMPOUNDS. 


EXERCISES. 

1.  Why  does  it  require  more  sugar  to  sweeten  fruits  when  the 
sugar  is  added  before  cooking  than  it  does  when  the  sugar  is  added 
after  cooking? 

2.  Write  the  symbol  for  dextrin. 

3.  Name  the  compounds  symbolized  as  follows  :  BaO,  Ba02,  Hg20, 
HgO,  FeS,  FeS2,  MnO,  Mn02  ,  Mn2O3,  FeO,  Fe2O3,  N80,  NO,  N203, 
N205,  N02,  P2S3,  P8SB,  SnCI2,  SnCI4,  FeBr2. 

4.  How  many  I.  of  Cl  are  required  for  the  complete  decomposition 
of  10  I.  of  olefiant  gas  ?  ff~  -/-  e   tfp  \#t}~*  *  { 

~   **'  (a'}  ^iye  the  reaction  in  the  preparation  of   C02.     (&.)   How 
'may  C02  be  distinguished  from  every  other  gas?    (c.)  How  much  of;' 
it  is  produced  by  burning  10  liters  of  marsh  gas  fT-f'uJfectf' 


ere 
obtained:  * 


6.  In  the  analysis  of  a  certain  compound,  the,  following  data  were 

^/l/u>        '  /^     4J-        U 

Oxygen..  ;  =  27.58 per  cent,  /"t 
Vapor  density,  4. 04,  on  the 


Carbon. . .  =  62.07 per  cent, 
Hydrogen.,  =  10.35 


air  standard. 

What  is  the  molecular  symbol  of  the  compound  ? 

7.  (a.}  Find  the  percentage  composition  of  marsh  gas.     (&.)  Of 
olefiant  gas. 

8.  What  weight  of  KCI03   is  necessary  to  the  preparation  of 
35,000  cu.  cm.  of  0  ?  (?&  '.'  V  •  «f 

9.  On  completely  decomposing,  by  heat,  a  certain  weight  of  KCI03; 
I  obtain  20.246  g.  of  KCI.     (a.)  What  weight  of  KCIO,  did  I  use  ? 
(b.)  What  volume  of  0  did  I  obtain  ? 

10.  To  inflate  a  certain  balloon  properly  requires  132.74  Kg.  of  H. 
What  weight  of  Zn  and  of  H8S04  will  be  needed  to  prepare  this 
quantity  of  H. 

11.  Write  the  name  and  a  graphic  symbol-for  H2S203,  introducing 
dyad  S  and  hexad  S. 

A       &L<\ 


§  232  SILICON.  201 


SILICON. 

%Or Symbol,  Si ;  atomic  weight,  28  m.  c. ;  quantivalence,  4. 
231.  Silicon. — Although  this  element  does  not  occur 
free  in  nature,  it  is  the  most  abundant  and  widely  diffused 
of  all  the  elements  except  oxygen.  Combined  with  oxygen 
alone,  as  silica  or  quartz,  or  with  oxygen  and  potassium  or 
sodium,  etc.,  as  metallic  silicates,  it  forms  a  large  part  of 
the  earth's  crust. 

(a.)  Free  Si  may  be  prepared  by  the  action  of  sodium  upon  potas- 
sium silico-fluoride. 

K2SiF6  +  2Na2  =  2KF  +  4NaF  +  Si. 

(&,)  Si  exists,  like  C,  in  three  allotropic  forms ;  as  a  soft,  brown, 
amorphous  powder  which  burns  easily  in  air  or  0,  forming  Si02  ;  as 
hexagonal  plates,  corresponding  to  graphite  in  lustre  and  electric 
conductivity;  as  needle  shaped  octahedral  crystals,  corresponding  to 
diamond  in  hardness.  These  octahedra  are  hard  enough  to  scratch 
glass. 

(c.)  The  only  acid  that  attacks  crystallized  Si,  is  a  mixture  of  HN03 
and  HF. 

(d.)  There  is  a  compound  of  H  and  Si  known  as  hy- 
drogen silicide  (SiH4)  that  is  somewhat  analogous  to  CH4. 
Similar  compounds  are  formed  with  members  of  the 
halogen  group,  as  SiCI4,  etc. 

232.  Silicon  Dioxide.— Silicon  has  only 
one  oxide  (silica,  silicic  anhydride,  Si02)«  It  is 
very  abundant  in  nature.  Its  purest  form  is 
quartz  or  rock  crystal,  which  is  found  in  beauti- 
ful hexagonal  prisms  terminated  by  hexagonal 


202  SILICON.  §  232 

pyramids.     Quartz  has  a  specific  gravity  of  2.6,  and  is  hard 
enough  to  scratch  glass. 

(«.)  Amethyst,  cairngorm-stone  and  rose  quartz  are  nearly  pure 
crystallized  Si02.  Agate,  carnelian,  chalcedony,  flint,  jasper,  onyx 
and  opal  are  nearly  pure  amorphous  Si02.  White  sand  and  sand- 
stone are  generally  nearly  pure  Si02.  Silicious  sand  and  sand-stone 
are  often  colored  yellow  by  an  iron  oxide. 

(&.)  Si02  is  insoluble  in  H20  or  in  any  acid  except  HF,  but  it  may 
be  dissolved  in  a  boiling  solution  of  potassium  or  sodium  hydrate. 
The  potassium  or  sodium  silicate  thus  formed  is  called  "  soluble 
glass"  or  "  water  glass."  Si02  is  dissolved  in  the  waters  of  some 
thermal  springs.  The  Geysers  of  Iceland  contain  dissolved  Si02, 
which  is  deposited  by  the  cooling  waters  upon  objects  immersed  in 
them.  Si02  melts  in  the  oxyhydrogen  flame  to  a  colorless  glass  that 
remains  transparent  when  cold. 

(c.)  Si02  from  the  soil  is  found  in  certain  plants,  especially  grains 
and  rushes.  The  outer  coat  of  rattan  contains  much  Si02,  as  does 
the  leafless  plant,  horse  tail,  which  is,  consequently,  used  for  polish- 
ing and  scouring. 

(d.)  Si02  is  also  found  in  animal  substances.  The  feathers  of  cer- 
tain birds  are  said  to  contain  40  per  cent,  of  SiCX. 

Experiment  217. — Place  a  few  cu.  cm.  of  concentrated  soluble  glass 
in  a  small  evaporating  dish  and  add  strong  HCI  until  the  mixture 
shows  an  acid  reaction.  A  thick  jelly  like  mass  will  be  formed  in  the 
liquid.  Place  the  dish  on  a  water  bath  and  evaporate  its  contents  to 
dryness.  Heat  this  solid  residue  gently  over  the  lamp.  It  will  di- 
minish in  volume.  Add  H20  and  filter.  The  insoluble  powder  left 
upon  the  filter  is  precipitated  Si023  one  of  the  lightest  known  pow- 
ders. This  jelly  like  mass  formed  in  this  experiment  probably  is 
silicic  acid  (H4SI04). 

233.  Natural  Silicates.— Silica  unites  with  many 
metallic  oxides  to  form  silicates.  The  natural  silicates  are 
very  numerous  and  many  of  them  are  of  a  very  complex 
composition.  Thus,  clay  is  a  silicate  of  aluminum ;  feld- 
spar is  a  double  silicate  of  aluminum  and  potassium; 
mica  is  a  triple  silicate  of  aluminum,  potassium  and  iron. 


§  234  SILICON.  203 

Experiment  218. — Add  some  HCI  to  a  dilute  solution  of  water  glass. 
NaCI  or  KCI  will  be  formed  with  H4Si04.  Pour  the  liquid  mixture 
into  a  dialyser,  made  of  parchment  paper  stretched  over  a  wooden 
ring  and  floated  on  the  surface  of  pure  H20.  The  chloride  solution 
passes  through  the  membrane  while  the  H4Si04  remains  dissolved  in 
the  dialyser. 

Crystallizable  substances,  like  NaCI  and  KCI  are  sometimes  called 
crystalloids,  and  uncrystallizable  substances,  colloids.  Crystalloids 
and  colloids  may  be  separated  as  in  this  experiment.  The  process 
is  called  dialysis. 

234:.  Artificial  Silicates.— Sodium  and  potassium 
silicates  (water  or  soluble  glass)  are  largely  used  in  the  arts. 
But  by  far  the  most  important  of  the  artificial  silicates  is 
glass,  which  is  a  mixture  of  a  silicate  of  sodium  or  of 
potassium,  or  of  both,  with  a  silicate  of  one  or  more  other 
metals.  The  composition  is  determined  by  the  desired 
infusibility,  insolubility,  transparency  or  color  of  the  glass. 

(a.)  Bohemian  glass  is  a  silicate  of  potassium  and  calcium.  It  is 
fusible  only  with  difficulty  and  is  but  little  acted  upon  by  chemical 
reagents.  It  is  free  from  color  and  is  largely  used  in  chemical  appa- 
ratus, especially  in  ignition  tubes. 

(5.)  Window,  crown  or  plate  glass  is  a  silicate  of  sodium  and  cal- 
cium. It  is  harder  than  Bohemian  glass,  but  more  easily  fusible  and 
more  readily  acted  upon  by  chemical  reagents. 

(c.)  Bottle  glass,  or  common  green  glass,  is  a  silicate  of  sodium, 
calcium,  aluminum  and  iron.  Its  color  is  due  to  the  iron  oxide  pres- 
ent as  an  impurity  in  the  cheap  materials  used.  It  is  harder  and 
more  infusible  than  window  glass,  but  more  easily  acted  upon  by 
acids. 

(<?.)  Flint  glass  is  a  silicate  of  potassium  and  lead.  It  has  a  high 
specific  gravity  (Ph.,  §  253)  and  great  refracting  power  (Ph.,  §  613,  a.). 
It  is  the  most  easily  fusible  variety  of  glass  and  is  easily  acted  upon 
by  chemical  reagents.  "  Crystal "  is  a  pure  flint  glass  used  for  opti- 
cal purposes.  "  Strass  "  is  a  flint  glass  very  rich  in  lead  and  having 
a  very  high  refractive  power.  It  forms  the  basis  of  the  artificial 
gems  and  precious  stones  known  as  "  paste." 

(e.)  Glass  softens  at  a  red  heat  and  can  then  be  readily  worked  and 
welded.  See  App.  4.  At  higher  temperatures  it  becomes  still  softer 


• 

204  SILICON.  §  234 

and  finally  melts.    On  cooling,  it  passes  from  a  thin,  mobile  liquid 
through  all  degrees  of  viscosity  to  a  hard  solid. 

(/.)  Glass  is  acted  upon  readily  by  HF(see  Exp.  126).  Etched 
glass  is  now  much  used  instead  of  the  more  expensive  cut  glass. 

(g.)  When  glass,  heated  almost  to  redness,  is  dipped  into  oil  heated 
to  800°C.  and  then  allowed  to  cool  gradually,  it  becomes  toughened. 
Table  glass  thus  toughened  is  not  readily  broken  by  falling  or  being 
thrown,  but  when  thrown  with  sufficient  force  to  break  it,  it  is 
shattered  into  minute  pieces. 

(A.)  Glass  is  easily  colored  by  the  addition  of  the  proper  materials 
to  the  fused  mass.  Thus,  a  green  color  is  produced  by  the  addition 
of  a  ferrous  or  cupric  oxide ;  blue,  by  a  cobalt  oxide  ;  violet,  by 
manganese  dioxide  ;  ruby,  by  gold,  etc.  C,  $"& 

j   \ 

.    _   .PXBECISES.          ^ 

ration  and  principal  properties  of  H2S,  CS2, 
HCN,  CH4,  C2H4andC2H60. 

2.  Write  the  symbols  representing  chloroform,  glycerine,  ether, 
acetic  acid,  cane  sugar  and  starch. 

3.  (a.)  Name  the  products  of  the  combustionNff  cST2  and  C8H60. 
(5.)  Describe  briefly  the  process  of  preparing  illuminating  gas  and 
tell  its  composition. 

4.  Name  the  substances  symbolized  as  follows:   KN02,    KNO3, 
K2S03,  K2S04,  HKS04,  KCI,  KCIO,  KCI02,  KCI03,  KCI04,  HNaS03, 
SiH4,  Si02,  H4Si04. 

5.  (a.)  Find  the  weight  of  20  1.  of  0.    (&.)  Of  50  I.  of  Cl.    (c.)  Of 
250^.ofNH3.  ,    . 

6.  What  materials  and  what  quantities  would  you  need  to  prepare 
50  I.  of  each  of  the  oxides  of  C  ? 

7.  By  heating  Mn03  with  H2S04  the  following  reaction  takes 
place : 

2Mn02  +  2H2S04  =  2MnS04  +  2H20  +  02. 

(a.}  What  weight  and  (&.)  what  volume  of  0  can  be  thus  obtained 
from  50  g.  of  Mn02  ?  7<£^$-u/  ^ 

8.  (a.)  Give  the  ordinary  methods   of  preparing  0,  H    and  HCI. 
(&.)  In  what  do  they  differ  and  in  what  do  they  agree  ?    (c.)  Find  the 

mount  of  Cl 

9.  If  100  I. 

tain  it,  from  what  materials,  and  what  quantity  of  each  material  ? 


,/7 


A,  ^ 

THE     NITROGEN     GROU  P. 


SECTION  i. 

PHOSPHORUS. 

Symbol,  P  ;  specific  gravity,  1.8  ;  atomic  weight,  31  m.  c.  ;  molec- 
ular weight,  124  m.  c. ;  quantivalence,  3  or  5. 

235.  Source.  —  Phosphorus  does  not  occur  free  in 
nature,  but  its  compounds  with  oxygen  and  some  metal 
(chiefly  calcium)  are  found  in  large  quantities.     Calcium 
phosphate  is  found  as  a  native  mineral ;  it  forms,  also,  the 
greater  part  of  the  mineral  constituent  of  animal  bone. 

(a.)  The  ultimate  source  of  P  is  the  granitic  rocks,  by  the  disinte- 
gration of  which  the  fertile  soil  has  been  produced,  All  fruitful 
soils  contain  some  of  the  phosphates,  but  diffused  in  such  small 
quantities  that  their  collection  thence  by  the  manufacturing  chemist 
would  be  very  costly.  Plants  collect  the  phosphates  from  the  soil  ; 
herbivorous  animals  obtain  them  by  consuming  the  plants  ;  from  the 
bones  of  animals,  the  chemist  derives  the  phosphates  from  which  he 
prepares  the  P  that  he  and  the  manufacturer  need.  The  process  is 
devious  and  complicated  but  the  greater  part  of  it  is  inexpensive. 

Note.— The  name  comes  from  two  Greek  words  that  mean  a  bearer 
of  light,  phosphorus  being  luminous  in  the  dark.  The  alchemists 
used  to  call  it  "  Son  of  Satan."  Phosphides  were  formerly  called 
phosphurets. 

236.  Preparation. — In  the  preparation  of  phos- 
phorus,  the    bones    are    burned  and  powdered.       This 


206 


PHOSPHOR  US. 


powdered  bone  ash  is  treated  for  about  twelve  hours  with 

two-thirds  its  weight  of 
strong  sulphuric  acid  di- 
luted with  about  twenty 
times  its  weight  of  water. 
This  treatment  yields  an 
insoluble  calcium  sulphate 
(gypsum,  CaS04)  and  a 
soluble  salt  called  "  super- 
phosphate of  lime."  The 
insoluble  sulphate  is  re- 
moved by  filtration.  The 
clear  solution  is  then  evap- 
orated to  a  sirupy  liquid, 
mixed  with  powdered  char- 
coal, dried  and  finally  dis- 
FIG.  96.  tilled.  The  long  neck  of 

the  earthen  retort  (Fig.  96)  dips  under  water  contained 
in  b.  The  liberated  phosphorus  distils  over  and  condenses 
under  the  water.  After  purification,  it  is  melted  under 
hot  water  and  run  into  cylindrical  moulds  placed  in  cold 
water. 


See  the  Caution  on  page  31,     Phosphorus  burns  are  very  dif- 
ficult to  heal. 

Experiment  219. — Bury  a  piece  of  P,  the  size  of  a  grain  of  wheat, 
in  a.teaspoonful  of  lamp-black  or  powdered  bone-black,  that  has  been 
freshly  prepared  or  recently  heated.  The  0  condensed  within  the 
pores  of  the  carbon  unites  with  the  vapor  of  the  P,  developing 
enough  heat  to  melt  and  finally  to  ignite  the  P. 

Experiment  S20. — Dissolve  a  piece  of  P  in  CS2.  Pour  some  of  the 
solution  upon  a  piece  of  filter  paper  placed  upon  the  ring  of  a  retort 
stand.  The  volatile  CS2  soon  evaporates,  leaving  the  P  in  a  finely 
divided  state  exposing  a  large  surface  to  the  oxidizing  influence  of 
the  air.  The  P  soon  bursts  into  flame,  which  only  partly  consumes 


§  237  PHOSPHORUS.  207 

the  paper.  The  burning  P  quickly  covers  the  paper  with  a  coat  of 
incombustible  and  protecting  varnish.  If  the  experiment  be  per- 
formed in  a  dark  room,  the  phosphorescence  will  be  very  marked. 

Experiment  221. — Rub  a  piece  of  dry  P  the  size  of  a  pin  head  be- 
tween two  bits  of  board.  The  heat  developed  by  the  friction  is  suf- 
ficient to  ignite  it. 

Experiment  222. — Heat  a  small  piece  of  P  in  a  dry  tube  with  a  mere 
trace  of  I.  Combination  promptly  takes  place,  a  small  quantity  of 
volatile  phosphoric  iodide  is  formed  and  the  rest  of  the  P  is  changed 
to  an  allotropic  form  known  as  red  phosphorus.  Try  to  repeat 
Exp.  221  with  red  P. 

Experiment  223. — Close  one  end  of  a  piece  of  narrow  glass  tubing 
about  30  cm.  long  by  fusing  it  in  a  flame.  In  the  ignition  tube 
thus  made,  place  a  small  bit  of  red  P  and  heat  it  gently  in  the  lamp 
flame.  A  yellow  coating  is  quickly  deposited  upon  the  cool  walls  of 
the  tube  not  far  from  the  heated  end.  Allow  the  tube  to  cool,  and 
cut  off  the  end  just  below  the  yellow  sublimate.  Scratch  this  yel- 
low deposit  with  a  wire  ;  it  will  take  fire,  as  it  is  ordinary,  yellow  P. 
By  heating  the  red  P,  a  part  of  it  burned,  thus  removing  the  0  from 
the  lower  part  of  the  tube.  The  inert  N  remaining  there,  enveloped 
and  protected  the  rest  of  the  P  from  combustion  and  thus  permitted 
its  reconversion  into  the  ordinary  variety. 

Experiment  221^.— Touch  a  slice  of  P  with  a  test  tube  containing 
boiling  H30.  The  P  will  be  ignited. 

Experiment  225.— Place  a  piece  of  P  under  H20  warm  enough  to 
melt  it.     Bring  a  current  of  O  from  the  gas-holder  into        . 
contact  with  the  melted  P.    The  P  will  take  fire  and  burn        1 0 
brilliantly  under  H20. 

Experiment  226—  Repeat  Exp.  3. 

237*  Physical  Properties.— Pure  phos- 
phorus is  an  almost  colorless,  translucent,  wax-  ::| 
like  solid.     The  ordinary  commercial  article  has 
a  feeble  yellow  tinge.     When  freshly  cut,  it  has    FlG-  97- 
a  garlic-like  odor,  often  hidden  by  the  odor  of  ozone,  which 
is  generally  present  when  moist  phosphorus  is  exposed  to 
the  air.     It  is  insoluble  in  water,  sparingly  soluble  in  tur- 


208  PHOSPHORUS.  §  237 

pentine,  petroleum  and  other  oils  and  easily  soluble  in  car- 
bon disulphide.  It  is  soft  and  flexible  in  warm  weather 
but  brittle  at  low  temperatures.  It  melts  at  44°C.,  form- 
ing a  viscid,  oily  liquid  which  boils  at  290°C.,  yielding  a 
colorless  vapor.  At  500°C.  the  vapor  is  62  times  as  heavy 
as  hydrogen.  Consequently,  its  molecular  weight  is 
124  m.  c.,  or  four  times  its  atomic  weight.  From  this  we 
conclude  that  the  phosphorus  molecule  contains  four  atoms 
and  that  each  atom  occupies  half  the  space  taken  up  by  a 
hydrogen  atom  (§  175). 

Experiment  227. — Upon  a  thin  slice  of  P,  place  a  crystal  of  I.  The 
two  elements  promptly  unite  with  great  energy,  leading  to  the  com- 
bustion of  the  excess  of  P. 

238.  Chemical  Properties.  —  Phosphorus  com- 
bines readily  with  many  of  the  elements,  especially  oxy- 
gen. It  undergoes  slow  combustion  at  ordinary  tempera- 
tures (forming  P203)  and  oxidizes  with  great  energy  at  u 
temperature  not  much  above  its  melting  point  (forming 
P205).  On  account  of  this  easy  inflammability,  phosphorus 
should  be  kept  and  cut  under  water  and.  never  handled  with 
dry  fingers.  Owing  to  its  slow  combustion,  it  is  feebly 
luminous  in  the  dark.  This  phosphorescence  is  a  familiar 
effect  of  a  futile  attempt  at  lighting  an  ordinary  friction 
match  in  a  dark  room.  In  distillation,  the  oxygen  in  the 
retort  must  be  replaced  by  some  inert  gas  like  hydrogen, 
nitrogen  or  carbon  dioxide.  Heated  for  several  hours  to 
about  240°C.,  out  of  contact  with  oxygen  or  any  other 
substance  capable  of  entering  into  chemical  union  with  it, 
it  is  changed  to  the  remarkable  allotropic  modification 
known  as  red  phosphorus. 

(a.)  The  difference  between  the  ordinary  yellow  and  the  red  varie- 
ties of  P  are  shown  in  the  following  table  : 


§  239  PHOSPHORUS.  209 

1.  Pale  yellow,  Chocolate  red. 

2.  Strong  odor,  Odorless. 

3.  Specific  gravity  =  1.83,  Specific  gravity  =  2.14. 

4.  Phosphorescent,  Not  phosphorescent. 

5.  Translucent,  Opaque. 

6.  Soluble  in  CS2,  Insoluble  in  CS2. 

7.  Subject  to  slow  combustion,  Exempt  from  slow  combustion. 

8.  Melts  at  44°C.,  Melts  at  255°C. 

9.  Changes    to    red  variety  at  |  changeg  to  yellow  variety  at  360oC> 

10.  Soft,  Hard. 

11.  Flexible,  Brittle. 

12.  Poisonous,  Not  poisonous. 

239.  Uses.  —  Phosphorus  is  extensively  used  in  the 
manufacture  of  friction  matches,  the  match  tips  generally 
being  a  mixture  of  phosphorus,  glue  and  potassium  chlo- 
rate. "  Safety  matches  "  are  tipped  with  an  timonous  sul- 
phide and  potassium  chlorate.  These  ignite,  not  by  simple 
friction,  but  by  rubbing  on  a  prepared  surface  containing 
red  phosphorus,  manganese  dioxide  and  sand.  Ordinary 
phosphorus  mixed  with  flour  paste  is  a  "  rat  poison  "  that 
has  probably  led  to  the  burning  of  many  houses.  Phos- 
phorus is  used  in  medicine ;  many  of  the  phosphates  are 
important  remedial  agents.  Phosphorus  fumes  produce, 
in  the  workmen  in  match  factories,  "phosphorus-necrosis, 
a  disease  in  which  the  bones  of  the  jaw  are  destroyed." 

(«.)  About  1200  tons  are  said  to  be  made  yearly,  nearly  all  of  it  at 
two  establishments,  one  near  Birmingham,  England,  and  the  other 
at  Lyons,  France.  The  manufacture  is  dangerous,  on  account  of  the 
easy  inflammability  of  the  product. 


.    210  PHOSPHORUS.  §  239 

EXERCISES. 

1.  (a.)  Symbolize  two  molecules  of  pentad  phosphorus.  Three  mole- 

•vi 

cules  of  quadrivalent  sulphur.  (&.)  What  do  S2  and  60" 2  represent  ? 

2.  (a.)  What  is  a  binary  molecule  ?    (6.)  A  ternary  molecule  ?    (c.) 
How  are  binary  molecules  named  ?    Illustrate. 

3.  How  much  P  is  contained  in  120  Kg.  of  bone  ash,  of  which 
_  £   ^88.5  #  is  Ca3(P04)2  and  the  rest  CaC03  ?     0 '1  /  X^//- 

4.  (a.)  Find  the  percentage  composition  of  carbon  monoxide.    (6.) 
Find  the  symbol  of   a  gas    having  the    composition  27.27%    C ; 
72.73$  O,  and  weighing  1.9712  g.  to  the  liter. 

5.  Red  oxide  of  copper  contains  88.8  parts  of  Cu  and  11.2  parts 
of  0,  by  weight.    Black  oxide  of  copper  contains  79.87  of  Cu  and 
20.13  of  0.     The  symbol  for  the  black  oxide  is  CuO  ;  what  is  the 
symbol  for  the  red  oxide? 

6.  What  is  the  meaning  of  the  following  : 

we  take  H30,  0<$g|]  will  remain. 

7.  Can  S2  and  S6  exist  at  the  same  temperature  ?    Explain. 

8.  Write  the  name  and  full  graphic  symbol  for 

(HO) -(SO,) -(SO,) -(HO).  ' 

+/-J-'  ' 


240 


PHOSPHOR  US    COMP  0  UNDS. 


211 


PHOSPHORUS    COMPOUNDS. 

24O.  Hydrogen  Phosphide.  —  This  colorless, 
poisonous,  ill-smelling  gas,  (phosphuretted  hydrogen, 
phosphine,  PH3;)  is  generally  prepared  by  heating  phos- 
phorus in  a  strong  alkaline  solution. 

(a.)  Dissolve  40  g.  of  potassium  hydrate  (caustic  potash)  or  60  g.  of 
freshly  slaked  lime  in 
110  cu.  cm.  of  H20.  Place 
it  in  a  flask  of  not  more 
than  200  cu.  cm.  capacity ; 
add  1  g.  of  P  in  thin 
slices,  and  5  or  6  drops  of 
(C2H5)20;  close  the  flask 
with  a  cork  carrying  a 
long  glass  delivery  tube 
that  terminates  beneath 
H20  as  shown  in  Fig  98. 
The  volatile  (C.2H3)20  is 
added  that  its  heavy  vapor 
may  force  the  0  of  the  air 
from  the  flask.  When  the 
contents  of  the  flask  are 
boiled,  gas  escapes  from  the  delivery  tube  and  bubbles  up  through 
the  H20.  As  each  bubble  of  gas  comes  into  contact  with  the  air,  it 
bursts  into  flame  with  a  bright  light.  If  the  air  of  the  room  be 
still,  beautiful  expanding  rings  of  white  smoke  (P805)  will  rise, 
with  vortex  motion,  to  the  ceiling. 

3KHO  +  P4  +  3H20  =  3KP(HO)2  +  PH3. 

(6.)  PH3  is  easily  formed  by  placing  calcium  phosphide  in  H20. 

(c.)  Two  other  compounds  of  H  and  P  are  known,  of  which  one  is 
liquid  and  the  other  solid  at  the  ordinary  temperature.  Their  proper 
symbols  have  not  yet  been  definitely  ascertained,  but  the  liquid  is 
generally  represented  by  PH3  or  PgH^  and  the  solid  by  P2H  or  P4H8. 


FIG. 


212 


PHOSPHOR  US    COMP  0  UNDS. 


§240 


(<?.)  Pure  PH3  is  not  spontaneously  combustible  in  the  air.  The 
combustion  above  noticed  is  due  to  the  presence  of  a  small  quantity 
of  P2H4.  If  the  gas,  as  it  comes  from  the  flask  (Fig.  98),  be  passed 
through  a  tube  chilled  by  a  freezing  mixture  (Ph.,  §  521,)  the  P2H4 
will  be  condensed.  The  escaping  PH3  will  not  take  fire  as  it  subse- 
quently bubbles  through  the  H20  and  comes  into  contact  with  the 
air. 

(e.)  The  composition  of  PH,  maybe  represented  by  the  accompany- 
ing diagram : 


1  m.  c.[ 


i    H    I 
i  1  m.  c.i 


,,.. 


It  may  now  be  noticed  that,  in  the  composition  of  the  compounds 
previously  studied,  the  weight  of  a  unit  volume  has  been  the  atomic 
weight  but  that  in  the  case  of  P  the  weight  of  half  a  unit  volume  is 
the  atomic  weight.  The  unit  volume,  being  half  the  molecular  vol- 
ume, would  include  two  P  atoms.  Compare  the  above  diagram  with 
the  one  given  for  NH3.  (§  70.) 

241.  Phosphorus  Oxides.  —  Theoretically,  there 
are  three  oxides  of  phosphorus,  having  the  symbols,  P20, 
P203,  P205. 

(a.)  P20  (hypophosphorous  oxide  or  anhydride,  phosphorus  mon- 
oxide) has  not  yet  been  isolated.  Its  compounds  are  known. 

(&.)  P203  (phosphorous oxide  or  anhydride,  phosphorus trioxide)  is 
formed  by  the  slow  coin  bastion  of  P  in  a  limited  current  of  dry  air. 
It  is  a  white,  amorphous  substance,  very  soluble  in  H20  and  burns 
in  the  air  to  P205. 

(c.)  P205  (phosphoric  oxide  or  anhy- 
dride, phosphorus  pentoxide)  is  formed 
by  the  rapid  combustion  of  P  in  an  ex- 
cess of  0.  Place  a  piece  of  thoroughly 
dry  P,  weighing  0.5  g.  to  1  g.  in  a  small  dry 
capsule  ;  place  the  capsule  upon  a  large, 
dry  plate ;  ignite  the  P  with  a  hot  wire 
and  quickly  cover  it  with  a  dry  bell  glass 
or  wide  mouthed  bottle  of  2  or  3  liters 
capacity.  The  capsule,  plate  and  bell 
glass  should  be  warmed  to  insure  their 
FIG.  99.  keing  drv-  The  P2°5  ^i"11  be  deposited 

as  a  white  fleecy   powder.    It  absorbs 


§242 


PHOSPHOR  US    C'OMP  0  UXDS. 


H20  with  great  eagerness,  and  is  sometimes  used  for  drying  gases. 
If  left  in  the  air,  it  deliquesces  completely  in  a  few  minutes  ;  if 
thrown  into  H20,  it  hisses  like  a  hot  iron  and  dissolves  with  the  evo- 
lution of  much  heat.  It  may  be  kept  in  dry  tubes  sealed  by 
fusion. 
In  preparing  large  quantities  of  P805,  the  following  process  may 


FIG.  100. 

be  used.  A  is  a  large,  dry  glass  globe  with  three  necks,  as  shown 
in  Fig.  99.  The  flexible  tube,  ?,  being  connected  with  an  aspirator, 
a  strong  current  of  air  is  drawn  through  the  drying  tube,  /,  into  the 
globe.  A  straight  glass  tube,  closed  at  the  upper  end  with  a  cork, 
passes  through  the  neck,  a,  and  carries  a  small  crucible  suspended 
near  the  centre  of  the  globe.  A  piece  of  P  is  dropped  through  the 
tube  into  the  crucible  and  ignited  with  a  hot  wire ;  the  tube  is  then 
corked.  The  current  of  air  being  maintained,  the  P  is  soon  burned 
to  P305.  Other  pieces  are  dropped  into  the  crucible  from  time  to 


time  to  render  the  process  continuous, 
over  into  B. 


Part  of  the  P205  is  carried 


242.  Phosphorus  Acids.— Phosphorus  combines 
with  oxygen  and  hydrogen  to  form  a  remarkable  series  of 
acids,  as  follows : 


214  PHOSPHoitrs    coMroi'Mts.  S  242 


P20(?)  -f     3H80  =  2H8P02,  hypophosphorous  acid. 
P80a     +     3H20  =  2H.,PO.j,  phosphorous  acid. 

rlJH.,0  =  2H3PO  4,  phosphoric  acid  (ordinary  or  tribasic). 
P205     +  -]2H80  =  H4PS07,  pyrophoKphoric  acid. 

(    HaO  =  2HPOa,  metaphosphoric  acid. 

(a.)  HgPOj,  gives  a  series  of  salts  known  as  hypophosphites  ;  e.  ff., 
sodium  hypophospbite,  HsNaPOs.  When  heated,  it  decomposes  into 
H3P04  and  PH3.  It  is  monobasic. 

(6.)  H3P08  may  be  formed  by  the  action  of  H20  on  P303,  by  the 
slow  oxidation  of  P  in  moist  air  or  by  the  decomposition  of  phos- 
phorus trichloride  by  HaO  :  PCI3  +  3H20  =  H3PO'3  +  3HCI.  When 
heated,  it  decomposes  into  H3P04  and  H:,P.  It  is  a  tribasic  acid  and 
forms  a  series  of  salts  known  as  phosphites  ;  e.  g.t  normal  sodium 
phosphite,  Na8P00  ;  tri-ethyl  phosphite*  (>CJ,H5)'3P03. 

(c.)  H3P04  may  be  prepared  by  tho  direct  union  of  P205  and  boil- 
ing HB0,  but  the  usual  process  is  to  oxidize  red  P  with  strong  HN03 
or  ordinary  P  with  dilute  HNO3.  When  heated,  it  changes  to  H4PBO7 
or  H  P03>  as  explained  below.  It  is  tribasic,  and  yields  normal,  double 
and  acid  phosphates  in  great  variety.  This  acid  is  sometimes,  with 
questionable  propriety,  called  orthophosphoric  acid.  It  and  its  salts 
arc  the  most  important  of  the  phosphoric  series. 

(d.)  H4PS0T  is  formed  by  heating  H3P04  to  215T.,  thus  depriving 
it  of  H20  :  2H3P04  —  H80  =  H4P2O7.  It  is  tetrabasic  and  yields 
normal,  double  and  acid  pyrophosphates  in  great  variety.  The  group, 
PO  (phosphoryl)  acts  as  a  trivalent  compound  radical.  The  equation 
above  may  be  written  graphically  as  follows  : 


From  Xw  tuke  H-°-H  and         ^O     remains 

(PO>/OH  <P<OH 

XOH 

(e.)  HP03  is  formed  by  the  direct  union  of  P3O6  and  cold  H80,  or 
by  heating  H3PO4  to  redness,  thus  depriving  it  of  H20  :  H3P04 
—  H80=HP03.  It  is  monobasic  and  yields  only  normal  meta- 
phosphates.  It  is  sometimes  called  glacial  phosphoric  acid.  If  its 
aqueous  solution  be  boiled,  it  yields  H3PO.,. 

Note.  —  For  theoretical  reasons,  the  purely  hypothetic*!  compound, 
H6P06,has  been  conceived.  Such  a  compound  would  be  properly 
called  0rMy>phosphoric  acid. 


§  242  ruosp  nours   COMPOUNDS.  215 

EXERCISES. 
&T  For  List  of  Elements  and  their  Symbols  see  Appendix  1. 

1.  What  is  the  apparent  quanti valence  of  P  in  P205  ?    Represent 
this  molecule  by  its  graphic  symbol. 

2.  (a.)  What  is  the  name  of  Ca"3(P04)o  V    (b.)  Why  may  not  the 
symbol  be  written  CaP04  ? 

3.  Choose  between  HNa'P04  and  HNa2P04.     Give  a  reason  for 
your  choice.  // <u . 

4.  Write  the  empirical  and  graphic  symbols  for  the  oxide  of  P'". 

5.  The  symbol  for  "microcosmic  salt"  is   HNa(NH4)P04.      (a.) 
What  is  the  systematic  name  of  the  salt?    (b.)  Is  it  a  normal  salt? 
Why  ?    (c.)  Write  the  symbol  of  the  corresponding  acid,    (d.)  What 
is  the  basicity  of  that  acid  ? 

6.  Symbolize  hydrogen  disodium  phosphate  and  dihydrogen  sodium 
phosphate,  and  normal  sodium  pyrophosphate." 

7.  What  is  the  systematic  name  of  the  sodium  salt  of  monobasic 
phosphoric  acid  ? 

8.  If  2  I.  of  PH3  were  decomposed,  what  volume  of  P  vapor  would 
it  yield? 

9.  («.)  Why  is  it  that,  while  an  atom  of  P  is  only  31  times  as 
heavy  as  an  atom  of  H,  a  liter  of  P  vapor  is  62  times  as  heavy  as  a 
liter  of  H  ?    (&.)  How  many  criths  will  a  liter  of  P  vapor  weigh  ? , 

10.  («.)  Is  Na'3P04  an  acid  salt?    Why?    (b.)  Is  it  a  double  salt? 
Why?    (c.)  Is  it  a  normal  salt?    Why?     (d.)  Is  it  a  salt  at  all? 
Why? 

11.  Can  you  write  the  symbol  for  hydrogen  sodium  metaphosphate  ? 

12.  (a.)  Read  the  equation  :  2Ag'nP04  +  3H2S=  2H3PO4  +  3Ag.,S. 
(&.)      «  •«     ,     Ag4P.,07  +  2H2S  =  H4P207  +  2Ag2S. 
(c.)      "  "          2  AgP03  +  H,S  =  2HP03  +  Ag2S. 

13.  Considering  the  silver  salts  symbolized  in  Exercise  12  to  be  in 
aqueous  solution,  summarize  the  teaching  of  these  three  reactions 
with  reference  to  the  formation  of  phosphoric  acids. 

14.  If  one  atom  of  0  in  a  molecule  of  metaphosphoric  acid  be  ra 
placed  by  two  of  H,  what  will  result  ?     $ 

15.  What  is  represented  by  O  =  P=  ?    % 

16.  Write  the  reaction  for  the  combustKm  of  one  molecule  of  P, 
in  an  excess  of  0. 

17.  Ca"3P2  +  5HCI  -  3CaCI2  +2.       .     Complete  the  equation. 

18.  Write  the  reaction  for  the  decomposition  of  H3P02  by  heat. 

19.  What  is  the  difference  between  a  phosphide  and  a  phesphuret? 
30.  Read:  Pb"3(P04)3  +  3HaS04  =3PbS04  +  2H3P04. 


216  PHOSPHORUS    COMPOUNDS.  §  2^2 

21.  The  tube  represented  in  Fig.  101  has  a  fine-  opening  at  a,  burning 

so  that  a  current  of  air 
may  be  drawn  through 
the  apparatus.     What  is  the  product  of  the  combustion  ? 

22.  I  have  a  substance  insoluble  in  carbon  disulphide  bufwhich 


causes  HN03  to  give  off  red  fumes,  and  forms  with  it  H3P04.  What 

is  the  substance  V    What  are  the  red  fumes  ?  '•$  ™  ^ 

23.  (a.)  If  from  the  imaginary  double  molecule,  2H5P05,  we  take 
2H  2O,  what  will  remain  ?    (6.)  What,  if  we  take  8H  20  ?    (<?.)  What, 
if  we  take  4H20  ?    (d.)  What,  if  we  take  5H20  ? 

24.  (a.)  If  in  a  molecule  of  tribasic  phosphoric  acid,  one  of  the 
univalent  hydroxyl  groups,  (HO)',  be  replaced  by  an  atom  of  H,  what 
will  result  ?    (&.)  What,  if  two  such  groups  be  replaced  by  H  2  ? 

25.  If  a  liter  of  PH  3  be  decomposed  by  the  passage  of  a  series  of 
electric  sparks,  what  volume  of  H  will  it  yield  ? 

26.  Write  empirical  and  typical  symbols  for  phosphorus  trihy- 
drate  and  phosphoryl  trihydrate.  /V}  /^j/v£/ 

27.  (a.)  What  is  the  apparent  quantivalence  of  P  in  H3P03  ?    (&.) 
InH3P04?  g    i 

28.  Give  the  name  of  the  compound  graphically  symbolized  as 
follows  : 

(HO)-P-O-(HO) 

&    *        • 

(HO)  —  P  —  0  —  (HO) 

29.  What  does  the  above  graphic  symbol  intimate  concerning  the 
quantivalence  of  the  P  ?  ' 

30.  Give  the  empirical  symbol  for  the  compound  graphically  sym- 
bolized as  follows  : 


31.  What  does  this  last  graphic  symbol  intimate  concerning  the 
quantivalence  of  the  P  ?     $. 

32.  Write  the  symbol  for  hypophosphorous  acid  upon  the  ammonia 
type. 

33.  What  weight  of  P  in  10  1.  of  PH3  under  normal  conditions  ?/  -J 

34.  (a.)  How  many  cu.  cm.  of  NH3  can  be  obtained  from  53.5  g.  of 
NH4CI?    (&.)  How  many,  under  the  conditions,  15°C.  and  740  mm. 
(Ph.,  §494.)  ;Af  — 


,|W 

' '  I  I 

'-  ^" 


§  245  ARSENIC   AND    ITS    COMPOUNDS.  217 


ARSENIC    AND     ITS    COMPOUNDS. 


Symbol,  As ;  specific  gravity,  5.6  to  5.9  ;  atomic  weight,  75  m.  c,  ; 
molecular  weight,  300  m.c.  ;  quantivalence,  3  or  5. 

243,  Occurrence  and  Preparation.  —  Arsenic 
is  widely  distributed  in  small  quantities.    It  is  sometimes 
found  free  in  nature  but  more  frequently  combined  with 
iron,  sulphur  and  other  elements.    It  is  generally  prepared 
from  arsenical  pyrite  (mispickel,  FeSAs)  by  sublimation  or 
from  its  oxide  by  reduction  with  charcoal. 

244,  Properties  and  Uses.— Arsenic  has  a  metal- 
lic lustre  and  a  steel-gray  color.    Its  vapor  is  150  times  as 
heavy  as  hydrogen.     In  its  physical  properties,  it  closely 
resembles  a  metal  ;  in  its  chemical  properties,  it  more 
closely  resembles  a  non-metal.    It  has  been  called  « the 
connecting  link  "  between  the  metallic  and  the  non-metal- 
lic elements,  being  closely  connected  with  antimony  and 
bismuth  on  the  one  hand  and  with  phosphorus  and  nitro- 
gen on  the  other.     Like  phosphorus,  its  molecule  contains 
four  atoms,  as  is  shown  by  the  specific  gravity  of  its  vapor 
(§  237).     It  and  almost"  all  of  its  soluble  compounds  are 
active  poisons.    Heated  in  the  air,  it  burns,  forming  the 
trioxide.     It  is  used  in  the  manufacture  of  shot  and  of 
fireworks. 

Note. — The  "  arsenic  ''  or  "white  arsenic"  of  the  druggist  is  ar- 
senic trioxide  (As303).  For  the  detection  of  As,  see  §  246.  The  ar- 
senides were  formerly  called  arseniurets. 

245,  Hydrogen  Arsenide. — This  very  poisonous 
gas  (arsine,  arseniuretted  hydrogen,  AsH3)  may  be  formed 

by  the  action  of  dilute  sulphuric  acid  upon  zinc  arsenide 
10 


218 


ARSENIC    AND    ITS    COMPOUNDS. 


§245 


The  greatest  care  must  be  taken  in  its  preparation, 
as  a  single  bubble  of  the  gas  has  been  "known  to  produce 
fatal  poisoning.  It  is  produced,  in  an  impure  state,  when 
a  solution  of  arsenic,  or  of  any  arsenic  compound,  is  acted 
upon  by  nascent  hydrogen.  When  burned  in  the  air,  it 
yields  water  and  arsenic  trioxide.  Its  volumetric  compo- 
sition is  similar  to  that  of  hydrogen  phosphide. 
Note. — A  solid  compound,  H2As2,  is  known  to  chemists. 

Experiment  228. — Arrange  the  apparatus  for  the  preparation  of 
dry  H,  using  a  cold  mixture  of 
1  part  of  H2S04  and  3  parts  of 
H20.  It  is  well  to  keep  the  gen- 
erating flask  cool  by  placing  it  in 
a  cold  water  bath.  When  the  air 
has  been  expelled  from  the  appa- 
ratus, ignite  the  jet.  Hold  a  piece 
of  cold  porcelain  in  the  flame,  and 
notice  that  no  colored  stain  is  pro- 
duced. (If  a  stain  should  appear, 
it  would  show  that  the  materials 
used  in  the  generating  flask  were 
impure.)  Keep  the  jet  burning  and  ^ 
add,  through  the  funnel  tube,  a 
few  drops  of  a  hot  aqueous  solution 
of  As203.  Notice  the  change  in 
the  appearance  of  the  flame.  Hold  the  cold  porcelain  in  the  flame. 
A  stain  having  a  metallic  lustre  will  be  produced.  The  stain  is 
metallic  As,  freed  from  combination  in  AsH3  by  the  heat  of  the  flame 
and  deposited,  just  as  soot  would  be  by  a  candle  flame.  Do  not  let 
the  porcelain  become  hot  enough  to  vaporize  the  As,  and  cause  the 
stain  to  disappear.  Keep  the  jet  burning  until  the  apparatus  is  placed 
in  the  ventilating  closet  or  out  of  doors,  to  prevent  the  escape 
of  AsH3. 

Experiment  229.— Clean  the  generating  flask  ar.d  repeat  the  experi- 
ment, using  "  Paris  green  "  instead  of  the  As00:!. 

Erperlmcnt230.—Bo\\  a  green  paper  label  with  HCI  in  a  test  tub?. 
Test  this  solution  for  the  presence  of  As,  as  in  Exp.  228.  Try  the 
same  with  green  wall  paper  or  with  green  paint  scraped  from  wood 
work. 


FIG.  102. 


§247  ^ARSENIC    AND    ITS    COMPOUNDS.  219 

Note. — The  author  has  often  demonstrated  the  presence  of  As  in 
green  fabrics  worn  as  clothing  in  his  classes. 

Experiment  231, — After  passing  the  AsH3  through  a  drying  tube 
containing  potassium  hydrate  and  calcium  chloride,  heat  the  glass 
tube  to  a  red  heat.  The  gas  will  be  decomposed,  the  As  being  de- 
posited as  a  dark  band  upon  the  cool  part  of  the  tube  and  the  H  burn- 
ing with  its  characteristic  flame  at  the  jet.  Little  or  no  deposit  will 
then  be  made  on  cold  porcelain. 

Experiment  832. — To  show  that  the  stains  produced  in  Exps.  228- 
229  are  As  and  not  Sb,  which  might  imitate  them,  touch  one  of  the 
stains  with  a  glass  rod  dipped  into  a  solution  of  chloride  of  lime. 
If  the  metal  dissolves,  it  is  As  and  not  Sb. 

246.  Marsh's  Test.  —  The  preceding  experiments 
rudely  illustrate  Marsh's  test  for  arsenic.     The  test  is  so 
delicate  that  0.01  mg.  (~0  grain)  of  the  poison    may  be 
recognized  with  certainty.     In  examinations  of  great  im- 
portance, as  in  trials  for  murder  by  arsenical  poisoning, 
the  purity  of  all  materials  used  and  the  nature  of  the 
metallic  deposit  are  carefully  determined  by  confirmatory 
tests. 

Experiment  233. — Place  a  small  quantity  of  As20s  in  a  tube  of 
hard  glass  (Fig.  102)  about  10  cm.  long  and  hold  the  tube  in  a  slop 
ing  position  in  a  lamp  flame  until  the  powder  is  volatilized.  With 
a  magnifying  lens,  examine  the  walls  of  the  tube  where  the 
As203  has  condensed  ;  the  oxide  will  be  seen  to  be  brilliantly  crys 
talline. 

Experiment  234. — Make  the  tube  used  in  the  last  experiment  into 
an  ignition  tube  by  fusing  and  sealing  one  end  of  it  in  the  lamp 
flame.  In  the  bottom  of  the  tube  thus  formed,  place  a  little  (a  few 
mg.  only)  of  As203  and  above  it,  a  small  piece  of  charcoal,  as  shown 
at  c,  Fig.  102.  Holding  the  tube  horizontal,  heat  the  charcoal 
splinter  to  redness  ;  then  gradually  bring  the  tube  into  a  nearly 
vertical  position,  keeping  the  charcoal  red  hot  and  heating  the  tip  of 
the  tube  until  the  As203  is  vaporized.  The  vapor  will  be  reduced 
by  the  glowing  charcoal  and  a  brilliant  ring  of  metallic  As  will  ap- 
pear at  a. 

247.  Arsenic  Trioxide. — Arsenic  trioxide  (arseni- 
ous  oxide,  arsenious    anhydride,  white    arsenic,    As203) 


220 


ARSENIC    AND    ITS    COMPOUNDS. 


§247 


is  prepared  on  the  large  scale  by  roasting  arsen- 
ical ores  with  free  access  of  air.  The  white 
smoke  given  off  condenses  to  a  white  powder. 
It  occurs  in  three  varieties,  the  amorphous  or  vitre- 
ous, and  two  different  crystalline  forms,  rhombic 
and  octahedral.  It  is  isodimorphous  with  anti- 
mony trioxide.  It  is  feebly  soluble  in  water  but 
dissolves  more  readily  in  boiling  hydrochloric  acid 
and  freely  in  boiling  nitric  acid  or  alkaline  solu- 
tions. Heated  in  contact  with  air,  it  volatilizes 
without  change.  Heated  in  contact  with  carbon, 
it  gives  up  its  oxygen  and  is  reduced  to  metallic 
arsenic.  As  a  poison,  it  is  very  dangerous,  because  it 
has  no  warning  odor  and  scarcely  any  taste  and  be- 
cause very  small  quantities  (0.2  g.)  produce  death. 
Its  best  antidote  is  freshly  prepared  feme  hydrate 
(see  §  3G3  for  its  preparation),  which  forms  with 
it  an  insoluble  salt  and  thus  prevents  the  poison 
from  entering  the  system.  When  these  can  not  be 
quickly  obtained,  the  white  of  eggs  or  soap-suds 
should  be  administered  promptly.  Arsenic  tri- 
oxide is  largely  used  in  the  manufacture  of  pig- 
ments and  of  glass. 

Note.— In  1873,  nearly  6,000  tons  of  As.,O3  were  made  in 
England  alone,  more  than  a  third  of  which  was  made  at  a 
single  mine.  As  the  vapor  density  of  this  substance  is  198,  its 
molecular  symbol  is  sometimes  written,  with  apparent  propriety,As406. 

248.  Arsenic  Pentoxide.— Arsenic  pentoxide  (arsenic  an- 
hydride, As205)  may  be  obtained  by  oxidizing  the  trioxide  with 
nitric  acid,  evaporating  to  dryness  and  heating  nearly  to  redness.     It 
is  lees  powerfully  poisonous  than  the  trioxide. 

249.  Arsenic  Acids.  —  Arsenic  forms  a  series  of 
acids  that  presents  remarkable  analogies  to  the  phosphorus 
acids. 


FIG.  103. 


§  250  ARSENIC    AND    ITS    COMPOUNDS.  221 

As203       +  3H20  =  2H3As03,  arsenious  acid. 

{3H20  =  2H3As04,  tribasic  arsenic  acid. 
2H20  =    H4As207,  pyroarsenic  acid. 
H20  —  2H  As03,  metaarsenic  acid. 

(a.)  When  As203  is  dissolved  in  H80,  the  solution  gives  a  feebly 
acid  reaction  and  is  supposed  to  contain  H3As08.  The  corresponding 
salts  are  called  arsenites  ;  e.g.,  silver  arsenite,  Ag3As03. 

(6.)  H3As04  is  generally  prepared  by  treating  As303  with  HN03. 
The  commercial  form  is  a  liquid  with  a  specific  gravity  of  2,  from  which 
transparent  crystals  may  be  obtained  by  cooling.  As  it  is  tribasic,  it 
yields  three  series  of  arsenates  which  closely  resemble  the  corre- 
sponding phosphates  in  composition  and  crystalline  form.  Heated  to 
180°C.  it  loses  H20  and  becomes  H4As207.  Heated  in  200°C.  it  loses 
another  molecule  of  H20  and  becomes  HAs03. 

Note. — As303  is  sometimes  improperly  called  arsenious  acid.  Less 
frequently,  but  with  equal  impropriety,  As205  is  called  arsenic  acid. 
Every  acid  contains  H. 

25O,  Sulphides  of  Arsenic.  —  Two  native  sul- 
phides of  arsenic  are  found.  The  red  sulphide  (As2S2)  is 
called  realgar ;  it  is  used  in  making  fireworks.  The  yel- 
low sulphide  (As2S3)  is  called  orpiment;  it  is  used  as  a 
pigment.  In  addition  to  the  disulphide  and  the  trisul- 
phide,  a  pentasulphide  (As2S5)  is  obtained  by  fusing  the 
trisulphide  with  sulphur. 

EXERCISES. 

1.  Write  the  equation  representing  the  combustion  of  hydrogen 
arsenide.  ,'  "•• 

2.  What  is  the  weight  of  10As203  ?  V'#*~  • 

3.  Name  the  following:  H3As04  ;  H2NaAs04  ;  HNa2As04  ;  Na3AsO4  ; 
(NH4)Mg"As04. 

4.  Write  a  graphic  symbol  for  H3P"'03. 

5.  When  AsH3  is  prepared  from  Zn2As3  and  dilute  H2S04,  ZnS04 
is  produced.     How  much  AsH3,  by  weight  and  by  volume,  can  be 
prepared  from  50  g.  of  Zn2As3  ? 

C.  (a.)  Why  is  As20s  said  to  be  dimorphous?  (&.)  Why  is  it  said  to 
be  isodimorphous  with  Sb203  ?  • 

7.  What  is  a  dyad  ?    A  monobasic  acid  ? 

S.  You  are  given  a  mixture  of  ordinary  and  red  phosphorus.  How 
will  you  separate  the  two  varieties  ? 


222  ANTIMOXY,    BISMUTH,    ETC.  §  251 


ANTIMONY,     BISMUTH,     ETC. 

ANTIMONY:    symbol,  Sb  (see  App.  1);  specific   gravity,  6.7; 
atomic  weight,  122  m.  c. ;  quantivalence,  3  or  5. 

251.  Source  and  Preparation. — The  antimony 
of  commerce  is  obtained  from  the  mineral  stibnite,  which 
is  an    antimony  trisulphide   (gray  antimony,   antimony 
glance,  Sb2S3).     Antimony  is,  however,  found  native  and 
in  combination  with  other  elements   than  sulphur.     The 
stibnite  is  melted  with   about  half  its  weight  of  iron 
(Sb2S3  +  Fe3  =  3FeS  +  Sb2)  or  heated  with  coal  in  a 
reyerberatory  furnace. 

Experiment  235, — Make  two  moulds  by  boring  conical  cavities  in 
a  block  of  plaster  of  Paris.  See  that  the  mould  terminates  below  in  a 
sharp  point.  Make  two  or  three  clean  cut  grooves  in  the  sides  of  the 
moulds.  Into  one  mould,  pour  melted  lead  ;  into  the  other,  melted 
type  metal.  Eemove  the  casts  and  notice  that  the  lead  cone  is 
blunted  at  the  apex  while  the  type  metal  is  pointed  ;  that  the  ridges 
on  the  sides  of  the  lead  cone  are  ill  defined  while  those  on  the  sides 
of  the  type  metal  are  well  defined. 

The  lead  contracts  as  it  cools  and  thus  shrinks  from  the  mould. 
The  type  metal  is  composed  of  about  70  parts  Pb,  10  parts  Sn  and 
20  parts  Sb.  The  Sn  gives  it  toughness  and  the  Sb  hardness.  The  Sb 
tends  to  crystallize  as  it  cools,  thus  causing  the  type  metal  to  expand 
and  force  itself  into  every  part  of  the  mould  and  make  a  sharply  de- 
fined cast  (Ph.,  §  525). 

252.  Properties  and  Uses. — Antimony  is  a  blu- 
ish-white metal.     It  is  so  brittle  that  it  may  be  powdered 
in  a  mortar.     Its  crystalline  tendency  is   so  strong  that, 
when  it  is  cooling  from  the  melted  condition,  beautiful 
fern-like  figures  are  formed  on  the  free  surface  of  the 


§  253  ANTIMONY,    BISMUTH,    ETC.  223 

metal.  These  figures  may  be  seen  on  one  surface  of  al- 
most every  cake  of  antimony  found  in  commerce.  It 
melts  at  450°C. 

It  is  not  acted  upon  by  the  air  at  ordinary  temperatures 
but,  when  melted  in  contact  with  the  air,  it  rapidly  oxi- 
dizes. At  a  red  heat,  it  burns  with  a  white  flame  forming 
antimony  trioxide  (Sb203).  It  is  a  constituent  of  tartar- 
emetic  and  is  largely  used  in  the  arts  as  a  constituent  of 
type  metal,  britannia  metal,  pewter  and  other  valuable 
alloys. 

(a.)  Sb  is  strongly  attacked  by  Cl  (Exp.  88),  forming  SbCI3.  It  is 
not  acted  upon  by  dilute  HCI  orH8S04but  is  easily  dissolved  by 
aqua  regia.  HN03  acts  upon  it,  forming  insoluble  Sb305. 

Experiment  236.— Put  80  cu.  cm.  of  HCI,  10  or  12  drops  of  HN03 
and  0.5  g.  of  powdered  Sb  into  a  small  flask  and  heat  the  mixture 
gently  until  the  metal  is  dissolved.  Evaporate  the  solution  to  a 
thick  syrup,  the  so-called  "  butter  of  antimony." 

253.  Antimony  Compounds.— The  compounds 
of  antimony  correspond  closely  to  those  of  arsenic. 

(a.)  Hydrogen  antimonide  (stibine,  antimoniuretted  hydrogen, 
SbH3)  is  formed  when  a  soluble  compound  of  Sb  is  acted  upon  by 
nascent  H.  It  is  analogous  to  AsH3,  but  its  metallic  deposit  is  easily 
distinguished  from  that  of  the  latter  compound  by  its  darker  color, 
smoky  appearance,  non -volatility  and  other  tests  (Exp.  232).  Its 
combustion  yields  H20  and  Sb203. 

(&.)  There  are  three  known  oxides  of  Sb  represented  by  the  sym- 
bols Sb2O3,  Sb204  and  Sb2O5.  The  tetroxide  maybe  considered  & 
mixture  of  the  other  two :  Sb2O3  +  Sb2O5  =  2Sb204.  All  of  these 
oxides  form  acids.  The  trioxide  is  isodimorphous  with  arsenic  tri- 
oxide. 

(c.)  There  are  two  sulphides,  Sb2S3  and  Sb2S5.  They  unite  with 
alkaline  sulphides  to  form  sulpho-antimonites  and  sulpho-antimo- 
niates  (see  §  171). 

(<f.)  There  are  two  chlorides,  SbCI3  and  SbCI5.  The  trichloride  is 
a  soft  solid,  known  as  butter  of  antimony ;  the  pentachloride  is  a 
strongly  fuming  liquid. 


224  ANTIMONY,    BISMUTH,    ETC.  §  254 


BISMUTH:   symbol,  Bi  ;  specific  gravity,  9.8  ;   atomic  weight, 
210  m.  c.  ;  quanticalence,  3  or  5. 

254.  Source   and  Preparation.  —  Bismuth  is 
found  in  nature  free,  and  also  in  combination  with   sul- 
phur   and   other    elements.     Commercial    bismuth    was 
formerly  prepared  by  heating  the  ore  in  iron  tubes  sloping 
over  a  furnace.     As  this  process  yields  only  apart  of  the 
native  metal,  all  bismuth  ores  are  now  roasted  and  then 
smelted  in  a  pot  with  iron,  carbon  and  slag.     The  crude 
bismuth  is  drawn  off  in  a  melted  condition  from  the  bot- 
tom of  the  smelting  pot  after  the  layer  of  less  easily  fusi- 
ble "cobalt-speiss"  above  has  solidified.      Most  of  the 
bismuth  of  commerce  comes  from  Saxony  and  Bohemia. 

Experiment  S37.  —  Melt  2  or  3  Kg.  of  Bi  in  a  crucible.  Perforate 
the  covering  crust  that  forms  on  cooling  and  pour  out  the  still  mol- 
ten liquid  within.  When  cool,  break  the  crucible  to  obtain  a  view 
of  the  beautiful  Bi  crystals  thus  formed.  (Compare  Exp.  181.) 

255.  Properties  and  Uses.—  Bismuth  is  a  brittle, 
brilliant,  pinkish-white  metal.    Of  all  known  substances, 
it  is  the  most  diamagnetic  (Ph.,  §  310).    In  cooling  from 
fusion,  it  crystallizes  more  readily  than  any  other  metal. 
Its  crystals  are  nearly  cubical  rhombohedrons,  often  beauti- 
fully iridescent  from  the  film  of  oxide  formed  when  the 
crystals  were  still  hot.    It  melts  at  264°C.  and  expands 
•fy  of  its  volume  on  solidifying. 

In  dry  air  at  ordinary  temperatures,  it  is  unaltered,  but, 
when  strongly  heated,  it  burns  with  a  bluish  white  flame 
forming  bismuth  trioxide  (Bi203).  It  is  used  in  forming 
alloys  and  in  the  construction  of  thermo-electric  piles 
(Ph.,  §§  412-414). 

(a.)  Bi  is  acted  upon  readily  by  Cl.  Cold  HCI  and  HaS04  have  no 
action  upon  it.  Its  best  solvents  are  HN03  and  aqua  regi't. 


§256 


ANTIMONY,    BISMUTH,    ETC. 


225 


(6.)  There  are  four  oxides  of  B\,ma.:  Bi202,  Bi203,  Bi204,  Bi205. 

Experiment  238.—  Place  30  g.  of  Bi,  15  g.  of  Pb  and  15  g.  of  Sn  in 
boiling  H.,0.  Let  the  metals  remain  there  until  convinced  that 
none  of  them  can  be  thus  melted.  Then  place  them  in  an  iron 
spoon,  molt  them  together  and  pour  the  molten  mass  into  cold  H20. 
Immerse  the  alloy  thus  formed  in  boiling  H20  and  notice  that  it  melts. 
Pour  the  liquid  alloy  into  a  small  test  tube  and  allow  it  to  cool. 
Notice  that,  after  several  minutes,  the  cooling  and  expanding  metal 
bursts  the  glass  walls  that  confine  it. 

256.  Fusible  Metals. — Bismuth  forms,  with  cer- 
tain other  metals,  alloys  that  melt  at  a  temperature  far 
below  the  melting  point  of  any  of  their  constituents. 
The  composition  and  melting  points  of  some  of  these  are 
given  in  the  following  table : 


Newton's 
Metal. 

Rose's 
Metal. 

Lichtenberg's 
Metal. 

Wood's 
Metal. 

8  parts, 

2 

5 

4 

Lead     

5    " 

1 

3 

2 

Tin  

3    " 

1 

2 

1 

Cadmium  .  .  »  

0    " 

0 

0 

1 

94°.5C. 

93°.75C. 

91°.  6C. 

60°  .50. 

These  melting  points  may  be  still  further  reduced  by  the 
addition  of  mercury.  It  will  be  noticed  that  any  of  these 
metals  will  melt  in  boiling  water.  If  any  of  these  melted 
alloys  be  poured  into  a  glass  vessel,  the  expansion  in  .solidi- 
fication will  burst  the  glass  when  the  metal  cools.  These 
alloys  are  used  in  obtaining  casts  of  woodcuts,  etc.,  the 
cast  being  made  when  the  metal  has  so  far  cooled  as  to  be 
viscid.  Lead,  tin  and  bismuth  are  mixed  in  such  propor- 
tions that  the  alloy  melts  at  some  particular  temperature 
above  100°C.  for  the  making  of  safety  plugs  for  steam 
boilers  (see  Ph.,  Fig.  270,  t}.  As  soon  as  the  steam  reaches 


226  ANTIMONY,    BISMUTH,    ETC.  §  256 

» 

the  pressure  corresponding  to  the  melting  point  of  the 
alloy  (Ph.,  §§  502,  509),  the  plug  melts  and  the  steam 
escapes. 

257.  The  Nitrogen  Group.— The  relations  of  the 
nitrogen  group  are  very  marked.  There  is  an  increase  in 
specific  gravity,  atomic  weight  and  metallic  characteristics 
from  nitrogen  to  bismuth  and  (in  a  general  way)  an  in- 
crease in  chemical  activity  from  bismuth  to  nitrogen. 

N.  P.  As.          Sb.  Bi. 

Specific  gravity.  .Gas,  1.8  5.7  6.7  9.8 

Atomic  weight. .  14  m.  c.      31  in.  c.     75  m.  c.    122  m.  c.   210  m.  c. 

Each  of  the  solids  crystallizes  in  two  forms  ;  i.  c.,  each  is 
dimorphous.  These  two  crystal  forms  are  the  same  for  the 
four  elements ;  i.  e.,  these  elements  are  isomorphous.  "We 
may,  then,  say  that  these  four  elements  are  iso-dimorphous. 

The  analogies  in  composition  and  properties  of  the  cor- 
responding compounds  of  the  members  of  this  natural 
group  are  very  significant.  Some  of  them  are  indicated 
below : 

Hydrides.  Trioxtdes.  Tetroxides.  Pentoxides.  Chlorides.  Sulphides.  Acids. 

NH3        N003        N204        No05        NCI3(?)  ....  HN03 

PH3         P203          ....          P-805         PCI3  P8S3  HP03 

AsH3        As2O3         As203        AsCI3  As2S3  HAs03 

SbH3        Sbo03       Sb304        Sbs08        SbCI3  SbBS,  HSb03 

Bi8~03       Bi204        Bi205        BiCI3  Bi8S3 

Note. — Closely  allied  to  the  metals,  antimony  and  bismuth,  are  the 
rarer  metals,  vanadium,  tantalum  and  columbium.  They  especially 
resemble  the  members  of  the  nitrogen  group  in  that  they  give  rise 
to  acid-forming  pentoxides. 


VANADIUM  :    symbol,  V  ;  specific  gravity,  5.5 ;  atomic  weight, 
51.2  m.  c. 

2«58.  Vanadium. — This  metal  is  an  extremely  rare  element, 
being  found  only  in  a  few  scarce  minerals.     Traces  of  it  are  found 


fc         #-'-i-    , 

°tjj 

§  260  ANTIMONY,     BISMUTH,     ETC.  221 

to  be  widely  distributed  throughout  the  earth  and  have  also  been 
found  to  exist  in  the  sun.  No  metal  is  more  difficult  to  prepare  than 
this,  on  account  of  the  great  affinity  of  the  metal,  at  a  red  heat,  for 
oxygen.  Every  trace  of  air  or  moisture  must  be  excluded  during  the 
preparation.  It  is  prepared  as  a  white  powder  with  a  brilliant,  crys- 
talline, silver  white  appearance.  It  forms  five  oxides,  analogous  to 
the  nitrogen  oxides:  V20,  V2O2,  V803,  V204,  V305. 


TANTALUM  :   sylribol,  Ta  ;   specific  gravity,   10.8  (?) ;   atomic 
weight,  182  m.  c. 

259.  Tantalum. — It  is  not  certain  that  this  metal  has  yet 
been  prepared  in  a  pure  state.  The  name  was  taken  from  the  mytho- 
logical Tantalus,  because  the  metal,  "  when  placed  in  the  midst  of 
acids,  is  incapable  of  taking  any  of  them  up  and  saturating  itself 
with  them."  Its  tetroxide  (Ta204)  and  pentoxide  (Ta205)  are  known. 
Tantalic  acid  has  the  composition,  HTa03. 


tEP**  COLUMBIUM  :  symbol,  Cb  ;  specific  gravity,  4-06  •  atomic  weight, 
94  m.  c. 

26O.  Columbilliii. — This  metal  is  generally  closely  associated 
with  tantalum.  It  has  been  obtained  as  a  steel  gray  solid.  It  yields 
a  dioxide  (Cb202),  a  tetroxide  (Cb204)  and  a  pentoxide  (Cb2O5). 
Columbic  acid  has  the  composition,  HCb03.  Columbium  is  some- 
times called  Niobium  (symbol,  Nb). 

EXERCISES. 

1.  Write  the  reaction  for  Exp.  88.  j£{  |  *  C»-     ^        'f 

2.  What  is  meant  by  the  statement  that  As203  and  Sb203  are 
isodimorphons  ? 

3.  When  a  current  of  H8S  is  passed  through  a  solution, of  SbCI, 
Sb2  S3  and  an  acid  are  formed.    Write  the  reaction.^  if  C  f-J  +  \ 

4.  Write  a  graphic  symbol  for  tribasic  phosphoric  acid,  represent- 
ing it  (a.)  as  a  compound  of  trivalent  P.    (&.)   As  a  compound  of 
pentad  P. 

5.  Write  a  graphic  symbol  for  hypophosphorous  acid  representing 
it  as  a  compound  of  trivalent  P.     As  a  compound  of  pentad  P. 

6.  (a.)  How  is  P2O5  made  ?    (&.)  How  many  distinct  phosphoric 
acids  can  be  formed  ?    Give  their  names  and  symbols. 

7.  (a.)  How  is  H2S04  made?    (&.)  State  the  difference  between 
Concentrated  and  fuming  sulphuric  acid. *,-• 

71 *— -,i/    v  fr 

' '        Mk\\    ^     ' I      ^* 

/ 


228  ANTIMONY,    BISMUTH,    ETC.  §  260 

8.  When  iodine  and  red  phosphorus  act  upon  each  other  in  the 
presence  of  H20,  the  reaction  may  be  represented  thus  :  J 


(a.}  What  weight  and  (&.)  what  volume  of  the  binary  acid  gas  can 
be  obtained  by  using  10  g.  of  P  ? 

9.  Explain  the  reaction  oi  sufficient  quantities  of  common  salt, 
Mn02  and  H3S04VS^A^;  'favQdit+M^ 

10.  What  is  a  microcrith  ?     What  is  quantivalence  ? 

11.  (a.)  What  is  a  chemical  compound  ?    (b.)  How  do  you  find  the 
combining  weights  of  compounds  ?    Illustrate  by  sulphuric  acid  and 
potassium  chlorate. 

12.  Give  the  symbols  and  names  of  two  common  compounds^pf  S 
with  one  chemical  and  one  physical  property  of  each.  $0*  [ 

13.  How  much  KN03  would  be  decomposed  by  630  #.  of  ^ 
and  how  much  H  N  0  3  would  be  formed  ?  6  7  ^  KN&j  • 

14.  When  anhydrous  magnesium  chloride,  MgCI2,  is  burned  in  air, 
a  white  powder  and  a  gas  are  produced.    The  powder  is  magnesium 
oxide  ;  the  gas  will  color  blue  a  strip  of  paper  wet  with  a  solution 
of  KI  and  starch.     Write  the  reaction. 

15.  When  barium  oxide,  BaO,  is  gently  neated  to  dark  redness  in 
the  air  it  is  changed  to  the  dioxide,  Ba02.     At  a  bright  red  heat  this 
decomposes  into  BaO  and  0.    How  may  these  facts  be  utilized  ? 


V, 

METALS    OF    THE    ALKALIES. 


SODIUM. 

261.  Metals. — The  metals,  gold,  silver,  copper,  iron, 
tin,  lead  and  mercury  were  known  to  the  ancients ;  the 
other  metals  have  heen  discovered  in  comparatively  recent 
times.  The  word,  metal,  is  not  capable  of  exact  defini- 
tion. At  one  time,  when  only  a  few  metals  were  known, 
they  could  be  easily  distinguished  from  the  non-metals  by 
their  high  specific  gravity  and  their  peculiar  metallic 
lustre.  But,  several  of  the  metals  now  known  float 
upon  water,  and  several  non-metallic  substances  have  the 
metallic  lustre.  Most  of  the  non-metals  are  electro-nega- 
tive and  form  acid  compounds,  while  the  metals  are  gen- 
erally electro-positive  (Ph.,  §  401)  and  form  basic  com- 
pounds. The  metals  are  generally  solid  at  ordinary  tem- 
peratures, malleable  and  good  conductors  of  heat  and 
electricity,  but  mercury  is  a  liquid  at  ordinary  tempera- 
tures. 

(a.)  The  elements  of  the  nitrogen  group  well  exhibit  the  gradual 
transition  from  the  distinctly  non-metallic  to  the  distinctly  metallic 
character.  N  is  an  unquestioned  non-metal  ;  R,  in  some  of  its  modi- 


230  METALS     OF    THE    ALKALIES.  §  26l 

fications,  closely  approaches  the  metals  ;  As  is  often  classed  as  a  semi- 
inetal ;  while  Sb  and  Bi  are  generally  classed  as  metals. 

(&.)  The  old  distinction  between  metals  and  non-metals  "  is  not 
founded  upon  any  real  or  essential  difference  of  properties,"  but  is 
preserved  for  the  sake  of  convenience. 

(c.)  It  will  be  well  to  remember  that  the  symbols  given  for  many 
metallic  compounds  are  not  necessarily  true  molecular  symbols. '  For 
example,  the  symbol  for  silver  chloride  may  be  AgCI  but  it  also  may 
be  Ag2CI2,  or  some  higher  multiple  of  AgCI.  Until  the  vapor  densi- 
ties of  these  metallic  compounds  are  determined,  we,  probably,  shall 
not  know  the  true  molecular  symbol  of  the  compound  or  the  true 
quanti valence  of  the  metallic  element. 


SODIUM:  symbol,  Na ;  specific  gravity,  0.97;  atomic  weight, 
23  m.  c. ;  quant  ivalence,  1. 

262.  Occurrence. — Free  sodium  is  not  found  in 
nature  because  it  unites  so  readily  with  the  elements  of  air 
and  water,  but  its  compounds  are  very  abundant  and  widely 
diffused.    Its  most  abundant  compound  is  sodium  chloride 
(common   salt,    NaCI),  from  which,   on   account  of    its 
abundance  and  cheapness,  nearly  all  of  the  sodium  and 
sodium  compounds  of  commerce  and  science  are  derived, 
directly  or  indirectly. 

(a.)  Sodium  nitrate,  carbonate,  borata  and  silicate  as  well  as  cryo- 
lite (§  120)  are  found  in  nature. 

263.  Preparation. — Sodium  was  first  prepared  by 
the  electrolysis  (Ph.,  §  397)  of  sodium  carbonate.    It  is 
now  extensively  prepared  by  igniting  a  mixture  of  sodium 
carbonate  and  charcoal. 

(a.)  30  Kg.  of  common  soda  ash  (§  268)  is  ground  up  with  13  Kg. 
of  coal  and  3  Kg.  of  chalk.     The  mixture  is  placed  in  an  iron  cylin- 


263 


METALS    OF    THE    ALKALIES. 


231 


der  1.2  long,  which  is  placed  in  a  furnace  and  heated  to  white- 
ness.    The  CO  and  the  Na  vapor  escape  through  the  delivery  tube 


FIG.  104. 

into  a  receiver  where  the  latter  condenses  and  whence  the  molten 
metal  flows  into  an  iron  vessel.    The  CO  is  burned  as  it  escapes. 

Na2C03  +  C2  =  Na2  +3CO. 

Experiment  239. — Wrap  a  piece  of  Na  in  wire  gauze  and  drop  it 
into  H3O.  Collect  and  test  the  gas  evolved. 

Experiment  2^0.— Fill  a  test  tube  with  mercury  and  invert  it  over 
that  liquid.  Thrust  a  piece  of  Na  into  the  mouth  of  the  tube  :  it 
will  rise  to  the  top,  Introduce  a  little  of  H20.  Explain  the  result- 
ing phenomenon  and  write  the  reaction. 

Experiment  241. — Throw  a  piece  of  Na,  the  size  of  a  pea,  on  cold 
H20.  It  swims  about,  decomposing  the  H  20,  freezing  the  H,  uniting 
with  the  0  and  then  dissolving  in  the  H20.  It  does  not  evolve 
enough  heat  to  ignite  the  H. 

Experiment  242. — Throw  a  piece  of  Na  upon  hot  H20, 
in  a  large,  loosely  stoppered  bottle.  The  liberated.  H  is 
ignited,  and  gives  a  yellow,  sodium-tinted  flame. 

Experiment  243- — Throw  a  piece  of  Na  upon  thick  starch 
paste.  The  liberated  H  burns  as  before,  the  paste  prevent- 
ing the  rapid  motion  of  the  globule. 

Experiment  244. — Melt  a  piece  of  Na  cautiously  under 
petroleum.  Notice  its  lustre.  FIG.  105. 


232  METALS    OF   THE    ALKALIES.  §  264 

Experiment  2Jfi. — Ignite  some  C2H60  in  a  small  saucer.  It  burns 
with  an  almost  colorless  flame.  Sprinkle  a  little  common  salt  into 
the  burning  liquid.  The  flame  becomes  yellow. 

Experiment  S46- — Wrap  a  piece  of  Na  in  cloth  or  filter  paper  and 
place  upon  a  piece  of  moist  ice.  Describe  and  explain*what  follows. 

264.  Properties  and  Uses.  —  Sodium  is  a  light 
metal  having  a  brilliant,  silver  white  lustre.     It  quickly 
oxidizes  in  moist  air  and  decomposes  water.    It  is  a  good 
conductor  of  heat  and  electricity,  in  which  respect  it  ranks 
next  to  gold  (Ph.,  §  539,  b).      It  is  best  kept  under  petro- 
leum or  in  a  liquid  or  atmosphere  free  from  oxygen.     It  is 
hard  and  brittle  at  —  20°C. ;  ductile  at  0°C. ;  soft  like  wax 
at  the  ordinary  temperature ;  semi-fluid  at  50°C.  and  melts 
at  96°C.     It  is  used  as  a  reducing  agent  in  the  prepara- 
tion of  silicon,  boron,  magnesium  and  aluminum.      Its 
amalgam  is  used  in  the  extraction  of  gold  from  quartzose 
rock  and  as  a  reducing  agent.     Its  salts  impart  a  yellow 
tinge  to  flame. 

265.  Oxide§. — Sodium  forms  two  oxides,  Na20  and  Na202. 

266.  Sodivini  Chloride.— Sodium  chloride  (com- 
mon salt,   NaCI)  is   obtained  by  mining  rock-salt  from 
natural  deposits  or   by  the  evaporation  of  saline  waters 
of  certain  mines,  springs  and  lakes  or  of  the  sea.     When 
the  concentrated  brine  is  rapidly  evaporated  by  boiling,  a 


FIG.  106. 

fine-grained  table  salt  is  produced ;  when  it  is  evaporated 
slowly,  a  coarse  salt  is  formed.  The  mother  liquor  from 
which  no  more  sodium  chloride  will  crvstallize  often  con- 


§  268  METALS    OF    THE    ALKALIES.  233 

tains  the  more  soluble  salts  of  calcium,  magnesium  and 
bromine  (§  115,  a.)  in  paying  quantities.  Sodium  chloride 
crystallizes  in  cubes,  the  edges  of  which  are  sometimes 
attached  so  as  to  form  hopper-shaped  masses.  Rock  salt 
is  usually  found  in  cubical  crystals,  is  highly  diatherma- 
nous  (Ph.,  §  552)  and  of  great  importance  in  physical  re- 
search. The  importance  and  many  uses  of  common  salt 
are  too  familiar  to  need  mention. 

267.  Sodium  Sulphate.  —  Sodium  sulphate  (Na2 
S04)  is  prepared  in  great  quantities  from  salt  and  sul- 
phuric acid  (see  §  74,  b.  and  §  105,  #.). 

(a.)  The  NaCI  and  H2S04  are  heated  in  large,  covered  pans.  The 
decomposition  of  NaCI,  in  the  first  stage  of  the  process,  is  only 
partial. 

2NaCI  +  H2S04  =  NaCI  +  HNaS04  +  HCI. 

The  HCI  is  absorbed  in  towers  filled  with  coke,  over  which  H20  is 
kept  trickling.  The  pasty  ma&s  is  then  strongly  heated. 

NaCI  +  HNaS04  =  Na2S04  +  HCI. 
The  HCI  is  absorbed  as  in  the  former  stage. 

(b.)  The  Na3S04  dissolves  easily  in  warm  H20.  When  such  a  con- 
centrated solution  cools,  ten  molecules  of  "  water  of  crystallization" 
are  taken  up  to  form  Glauber's  salt  (Na2S04,  10H30).  Exposed  to 
dry  air,  the  Glauber's  salt  effloresces  and  is  changed  to  Na2S04  by  its 
loss  of  H20.  (Ph.,  §  524,  3.) 

(e.)  Hydrogen  sodium  sulphate  (HNaS04)  is  often  called  sodium, 
di-sulphate  or  bisulphate  of  soda. 

268.  Sodium  Carbonate. — Sodium  carbonate  (sal- 
soda,  Na2C03)  is  made  in  immense  quantities  from  com- 
mon salt  by  the  Leblanc  process,  so  called  from  the  name 
of  its  inventor. 

(a.)  The  first  step  is  the  preparation  of  Na2S04  as  described  in  the 
last  paragraph.  The  Na2S04  is  then  heated  in  a  reverberatory  furnace 
with  an  equal  weight  of  calcium  carbonate  (chalk  or  limestone, 
CaC03),  and  about  half  its  weight  of  coal.  The  resulting  product  is 


234  METALS    OF    THE    ALKALIES.  §  268 

called  "black  ash,"  essentially  a  mixture  of  Na3C03  and  calcium 
sulphide.  The  soluble  parts  of  the  black  ash  are  extracted  with 
H20,  evaporated  to  dryness  and  roasted  in  a  furnace  with  sawdust 
and  sold  as  "  soda  ash."  This  soda  ash  contains  about  80  per  cent. 
of  Na2C03. 

(&.)  By  dissolving  soda  ash  in  hot  H20  and  allowing  the  solution 
to  cool  and  stand  for  several  days,  large  transparent  crystals  of  "  wash- 
ing soda  "  (soda  crystals,  Na2C03  +  10H30)  are  formed.  These  crys- 
tals part  with  their  water  of  crystallization  by  efflorescence  or  heat- 
ing. The  dry  residue  is  Na2C03  purified  by  the  process  of  crystalli- 
zation, one  of  the  most  valuable  known  means  of  purification. 

(c.)  Many  salts  owe  their  crystalline  form  to  the  presence  of  a  defi- 
nite number  of  molecules  of  H20,  which  may  be  driven  off  by  heat. 
These  aqueous  molecules  constitute  the  "  water  of  crystallization." 
When  soda  crystals  are  simply  exposed  to  the  air,  they  part  with 
their  water  of  crystallization  and  fall  to  a  white  powder  or  become 
coated  with  it.  The  crystals  are  then  said  to  "effloresce."  The 
opaque  white  powder  of  anhydrous  alum  combines  with  24  molecules 
of  H20  to  form  the  well  known  crystals  of  common  alum  [K2AI2 
(S04)4  +  24H30].  By  heating  these  crystals,  the  water  of  crystal- 
lization may  be  driven  off  and  the  anhydrous  salt  left  in  the  form  of 
a  powder. 

269.  Hydrogen  Sodium   Carbonate.— Hydro- 
gen sodium  carbonate  (soda,  sodium  bicarbonate,  HNaC03) 
is  easily  prepared  by  passing  a  stream  of  carbon   dioxide 
through  a  solution  of  sodium  carbonate  or  by  exposing 
soda  crystals  to  an  atmosphere  of  carbon  dioxide.     It  is 
used  in  medicine  and  in  cooking. 

Na3C03  +  H,0  +  C02  =  2HNaC03 
or Na2C03,10H,0  +  C02  =  2HNaC03  +  9H20. 

(a.)  When  solutions  of  HNaC03  and  of  cream  of  tartar  are  mixed, 
CO 2  is  set  free  and  the  purgative  Rochelle  salt  remains  in  solution. 

(&.)  When  cake  or  biscuit  is  raised  with  HNaCCX  and  cream  of 
tartar,  the  escaping  C03  renders  the  dough  light  and  Rochelle  salt 
remains  in  the  loaf. 

270.  Sodium  Hydrate.— Sodium  hydrate  (caustic 
soda,  sodium  hydroxide,  NaHO)  is  formed  when  sodium  is 


§  271  METALS    OF    THE    ALKALIES.  235 

thrown  upon  water,  but  in  practice  it  is  made  from  sodium 
carbonate.  It  is  a  white,  opaque,  brittle  solid  of  fibrous 
texture.  It  deliquesces  in  the  air,  absorbing  moisture  and 
carbon  dioxide  and  changing  thus  to  the  non-deliquescent 
carbonate,  the  coating  of  which  protects  the  hydrate  from 
further  loss.  It  is  a  strong  base,  a  powerful  cautery  and 
is  largely  used  in  the  manufacture  of  hard  soap.  An  im- 
pure variety  is  sometimes  found  in  commerce  under  the 
name,  "  concentrated  lye." 

(a.)  Na2C03  is  dissolved  in  boiling  H  20.     Cream  of  lime  (§  292)  is 
added  to  this  not  solution  until  it  is  free  from  C02. 


Na3C03  +  CaH203  =  2NaHO  +  CaC0 


3- 

The  insoluble  CaC03  is  removed  from  the  solution  of  NaHO  and 
the  latter  evaporated  until  an  oily  liquid  is  obtained.  This  liquid 
solidifies  on  cooling  and  is  usually  cast  in  the  form  of  sticks. 

(6.)  Caustic  soda  is  made  in  large  quantities  as  an  incidental  pro- 
duct of  the  manufacture  of  Na2C03,  being  cheaply  prepared  from  the 
liquor  from  which  the  "black  ash"  was  deposited. 

Experiment  247. — Make  a  strong  solution  of  NaHO  and  put  it  into 
a  retort  or  flask  with  some  granulated  Zn.  Heat  the  flask  over  a 
sand  bath  or  wire  gauze  until  the  liquid  boils.  A  gas  will  be  evolved. 
Collect  it  over  H20  and  find  out  what  it  is. 

271.  Other  Sodium  Compounds.— (a.) Borax  (Na2B407, 
10H20)is  sodium  bi-borate  or  sodium  pyroborate  (§1726).  It  is 
made  by  fusing  or  boiling  boric  acid  with  half  its  weight  of  soda- 
ash. 

(6.)  Sodium  nitrate  (Chili  nitre,  South  American  saltpetre,  NaN03) 
is  a  deliquescent  substance  found  in  the  soil  of  certain  parts  of  South 
America. 

EXERCISES. 

1.  Write  the  symbol  for  decahydrated  sodium  sulphate. 

2.  Write  the  symbol  for  anhydrous  sodium  carbonate,   jj 

3.  What  is  the  symbol  for  sodic  chloride?  \  \  /: 

4.  Write  the  graphic  symbol  for  the  disulphate  of  soda. 


236 


METALS    OF    THE    ALKALIES. 


5.  The  sodium  obtained  in  practice  being  one-third  the  theoretical 
yield,  what  weight  of  the  metal  can  be  prepared  from  \^Kg.  ojL  ^j 
sodium  carbonate ?/l^»&6> "^2^    i^A^T<Q&0  N      '^O,'^^-/*/*  X,  , 

G.  What  is  the  percentage  composition  of  NaN03  ? 

7.  What  weight  of  KCIOa  is  needed  to  furnish  enough  0  to  burn 
the  H  evolved  by  the  action  of  200  g.  of  Na  upon  H20  ? 

8.  (i.)  Find  the  weight  of  1  I.  of  each  of  the  following:  N,  C08, 
0,  CH4.    (&.)  Find  the  volume  of  1  g.  of  each. 

9.  Write  the  name  and  full  graphic  symbol  for 

(HO)  -  (SO,)  -  S  -  (S0t)  -  (HO)/ 


§  273  POTASSIUM.  237 


POTASSIUM,     ETC. 

Symbol,  K;  specific  gravity,  0.865;  atomic  weight ,39. 04  m.  c. ; 
molecular  weight,  78.08  m.  c.  ;  quantivalence,  1,  3  and  5. 

272.  Source.  —  Potassium    compounds    are    found 
widely  distributed  in  nature,  forming  an  essential  con- 
stituent of  many  rocks  and  of  all  fruitful  soils.     Potas- 
sium compounds  are  taken  from  the  soil  by  the  rootlets  of 
plants,  none  of  which  can  live  without  them.     It  is  essen- 
tial to  animal  life  also.    Free  potassium  is  not  found  in 
nature. 

273.  Preparation.— Potassium  is  prepared  by  heat- 
ing intensely  a  mixture  of  its  carbonate  with   charcoal. 

K2C03  +  C2  =  K2  +  3CO. 

(a.)  By  igniting  acid  potassium  tartrate  (crude  tartar)  in  a  covered 
iron  crucible  and  quickly  cooling  by  plunging  the  crucible  into  cold 
water,  the  desired  mixture  is  formed  as  a  charred,  porous  mass. 
This  mixture  is  then  heated  to  whitenass  in  a  retort,  when  K  vapor 
is  evolved,  rapidly  cooled  and  collected  under  petroleum.  The  pro- 
cess is  subject  to  the  danger  of  serious  explosions  from  the  tendency, 
at  the  high  temperature  employed,  of  the  K  vapor  and  the  CO  to 
form  an  explosive  compound,  K2C2O2. 

(&.)  K  may  be  prepared  on  the  small  scale  by  the  electrolysis  of 
equal  molecular  proportions  of  KCI  and  calcium  chloride.  These  sub- 
stances are  melted  together  over  a  lamp,  in  a  small  porcelain  crucible 
into  which  two  rods  of  gas  carbon  are  dipped.  These  rods  are  made 
the  electrodes  of  a  battery  of  six  or  eight  Bunsen  cells  (Ph.,  §§  877, 
333).  The  lamp  is  so  placed  that  the  salt  around  the  negative  elec- 
trode becomes  solid  while  that  around  the  positive  remains  liquid  to 
allow  the  escape  cf  the  Cl,  set  free  by  the  electrolysis.  After  pass- 
ing the  current  about  twenty  minutes,  the  crucible  is  cooled  and 


238 


POTASSIUM. 


§273 


opened  under  petroleum.  Pure  K  is  found  at  the  negative  electrode 
(Ph.,  §  401). 

Experiment  248. — Drop  a  piece  of  K,  half  the  size  of  a  pea,  upon 
H20.  It  decomposes  the  H 2 0,  the  H  burns 
with  a  flame  beautifully  tinted  with  the 
vapor  of  K.  If  the  H  20  be  in  an  open  dish, 
stand  at  a  distance  of  a  meter  or  more,  as 
the  combustion  will  terminate  with  a  slight 
explosion.  Test  the  H20  at  the  end  of  the 
experiment  with  reddened  litmus  paper. 

Experiment  249.— Stretch  a  piece  of  blot- 
ting paper  upon   a  wooden  tray,  wet  the 

paper  with  a  red  solution  of  litmus  and  throw  upon  it  a  small  piece 
of  Na  or  K.  The  track  of  the  metal  as  it  runs  over  the  moistened 
paper  will  be  written  in  blue  lines,  showing  the  formation  of  an  al- 
kaline product. 

Experiment  250.— Hold  a  small  piece  of  K  under  H20  by  means  of 


FIG.  108. 

wire  gauze  or  filter  paper.    Collect  the  gas  evolved  as  shown  in  the 
figure.     What  is  this  gas  ? 

Experiment  251, — In  Fig.  109,  a  represents  a  bottle  for  the  genera- 
tion of  CO.., ;  c,  a  drying  tubs,  containing  calcium  chloride  ;  e,  a  tube 
of  Bohemian  (hard)  glass  with  a  delivery  tube,  t,  dipping  into  the 
bottle,  i.  When  a  lighted  match  thrust  into  i  is  quickly  extinguished, 


§  274  POTASSIUM.  239 

we  may  know  that  the  apparatus  is  filled  with  C02.  Then,  dry  a 
piece  of  K  the  size  of  a  pea  by  pressing  it  between  folds  of  filter 
or  blotting  paper,  remove  t,  thrust  the  K  into  e  and  replace  t.  When 


FIG.  109. 

the  K  is  heated  by  the  lamp  flame,  it  will  burn,  taking  O  from  the 
CO  2  and  depositing  black  C  upon  the  walls  of  e. 

2K2  +  3C02  =  2K2C03  +  C. 

The  particles  of  black  C  may  be  made  more  evident  by  placing  e  in 
a  bottle  of  clear  H20,  to  dissolve  the  K2C03. 

Experiment  252.— Repeat  Exp.  249,  using  a  current  of  HCI  instead 
of  C02.  Collect  over  H20  the  gas  delivered  through  t.  What  is 
this  gas  ?  Write  the  reaction.  H C, 

Experiment  253. — Repeat  Exp.  250,  using  NH3  instead  of  HCI. 
Write  the  reaction. 

Experiment  25^. — Bore  a  half  inch  hole  two  inches  deep  in  a  block 
of  ice.  Enlarge  the  bottom  of  the  cavity  to  the  size  of  a  hickory  nut. 
Into  this  cavity,  drop  a  piece  of  K,  the  size  of  a  pea,  and  notice  the 
beautiful  volcanic  action.  Try  the  experiment  in  a  warm  and  dark- 
ened room. 

274.  Properties.— Potassium  is  a  light  inetal  hav- 
ing a  brilliant  bluish-white  lustre.  In  electro-positive 
characteristics,  it  ranks  third  among  the  metals,  and  in 
lightness,  second.  It  is  brittle  at  0°C. ;  soft  like  wax  at 
15°C.,  and  easily  welded  when  the  surfaces  are  clean  ;  it 
melts  at  about  63°C.  Its  physical  and  chemical  properties 


240  POTASSIUM.  §  274 

closely  resemble  those  of  sodium,  but  it  is  less  used  on  ac- 
count of  its  greater  cost.  Like  sodium,  it  is  best  kept 
under  petroleum.  Its  salts  communicate  a  violet  tint  to 
flame. 

275.  Oxides.— Potassium  forms  two  oxides,  K20  and  K204. 

276.  Potassium  Chloride.  —  Potassium  chloride 
(KCI)  is  found  in  sea  and  other  salt  waters,  and  is  largely 
prepared  from  the  mother  liquor  from  which  the  sodium 
chloride  has  crystallized,  and  from  the  Stassfurt  deposit  of 
carnallite  (KCI,  MgCI2,  6H20).     It  resembles  sodium  chlo- 
ride in  appearance  and  taste  but  is  more  easily  soluble  in 
water.      It  dissolves  in  about  three  times  its  weight  of 
water  at  the  ordinary  temperature,  producing  great  cold 
(Ph.,  §  521).      Like  sodium  chloride,   it  crystallizes  in 
cubes. 

(a.)  The  other  potassium,  halogen  salts,  KBr,  KI  and  KF,  alsocrys- 
tallize  in  cubes,  have  a  saline  taste  and  easily  dissolve  in  H2O,  KBr 
and  KI  are  used  in  medicine  and  in  photography. 

277.  Potassium  Cyanide.  —  Potassium  cyanide 
(KCN  or  KCy)  is  a  white,  fusible,  deliquescent  and  intensely 
poisonous  solid.    As  its  solution  dissolves  silver  and  gold 
cyanides,  it  is  largely  used  in  electro-plating  (Ph.,  §  399,  a). 
It  is  a  powerful  reducing  agent.    It  is  isomorphous  with 
potassium  chloride.     (See  Caution  preceding  Exp.  198.) 

278.  Potassium  Carbonate.— Potassium  carbon- 
ate (K2C03)  is  generally  prepared  in  this  country  by  leach- 
ing wood  ashes  to  form  potash-lye  and  evaporating  the  lye 
in  large  pots  or  kettles,  whence  the  name  of  the  crude 
article,  potash.      The  potash,  when  refined,  is  called  pearl- 
ash.    A  pure  carbonate,  prepared  by  igniting  the  bicar- 
bonate, is  called  salt  of  tartar.    Potassium  carbonate  is  a 
deliquescent  salt  with  a  strong  alkaline  taste  and  reaction. 


§  280  POTASSIUM.  241 

(a.)  K2C03  was  formerly  of  more  importance  than  now,  as  Le- 
blanc's  process  lias  rendered  Na2C03  so  much  cheaper  that  it  has 
largely  replaced  the  former  in  commerce  and  the  arts.  As  Kj,C03  is 
hygroscopic  and  Na2C03  is  not,  the  latter  is  much  more  convenient 
for  storing  and  handling. 

(&.)  As  Na.,C03  is  used  in  making  hard  soap,  so  K2COS  is  used  in 
making  soft  soap. 

(c.)  The  rapid  extinction  of  American  forests  has  greatly  checked 
the  manufacture  of  American  potash,  which  industry  is  now  not 
more  than  20  per  cent,  of  what  it  was  20  years  ago.  Similar  causes 
have  operated  in  Europe.  Hence,  other  sources  have  been  sought 
and  large  quantities  are  now  made  from  the  refuse  material  of  the 
beet-root  sugar  manufacture  and  also  from  K2S04  by  a  process  simi- 
lar to  the  Leblanc  process  for  preparing  Na3C03. 

279.  Hydrogen  Potassium  Carbonate.— Hy- 
drogen potassium  carbonate  (saleratus,  potassium  bicar- 
bonate, HKC03)  is  prepared  by  passing  a  current  of  carbon 
dioxide  through  a  strong  solution  of  potassium  carbonate. 

K8C03  +  H20  +  C02  =2HKC03. 

280.  Potassium    Hydrate.— Potassium   hydrate 
(caustic  potash,  potassium  hydroxide,  KHO)  is  prepared 
from  potassium  carbonate  as  sodium  hydrate  is  from  sodium 
carbonate.     Its  physical  and  chemical  properties  closely 
resemble  those  of  sodium  hydrate.     It  combines  with  fats 
and  oils  to  form  soft  soap,  and  is  one  of  the  strongest 
bases  known.  /fi<i^  +  (    }^^^ 

(a.)  As  KHO  absorbs  H20  and  C02  from  the  air,  it  is  gradually 
changed  to  K3C03.  As  this  salt  is  deliquescent,  the  change  goes  on 
until  all  of ,  the  KHO  is  changed  to  a  sirup  of  K2C03.  Consequently, 
it  should  be  kept  in  closely  stoppered  bottles.  It  is  usually  cast  in 
the  form  of  sticks. 

(&.)  KHO  is  easily  but  not  cheaply  prepared  by  the  action  of  K  upon 
H20. 

(c.)  A  solution  of  KHO  aiv.ckly  destroys  both  animal  and  vegetable 
substances.  It  is  best  c^rified  by  subsidence  and  decantation  though 
it  may  be  filtered  through  glass,  sand,  asbestus  or  gun-cotton. 


242  POTASSIUM.  §  28l 

Experimen t  255.— Repeat  Exp.  246,  using  KHO  instead  of  NaHO. 

Experiment  S56. — Repeat  Exp.  3. 

Experiment  2 57. — Repeat  Exp.  113. 

Experiment  258. — Repeat  Exp.  1.  The  mixture  may  be  placed  in 
a  paper  or  metal  cylinder  and  the  experiment  tried  in  a  dark  room 
with  good  effect. 

Experiment  259.— Carefully  mix,  with  a  feather,  a  small  quantity 
of  powdered  KCI03,  and  an  equal  quantity  of  powdered  red  P.  The 
mixture  will  ignite  when  struck  even  a  slight  blow  as  with  a  glass 
rod. 

Experiment  260. — Place  a  pinch  of  powdered  KCI03  and  one  of 
flowers  of  S  in  a  mortar  and  rub  them  together  with  the  pestle.  A 
series  of  explosions  will  take  place.  A  minute  quantity  of  the  same 
mixture  may  be  exploded  by  a  blow  of  a  hammer. 

281.  Potassium  Chlorate. —Potassium  chlorate 
(chlorate  of  potash,  KCI03)  is  largely  used  in  the  prepara- 
tion of  oxygen,  and  for  other  purposes  in  the  laboratory. 
It  is  also  used  in  medicine,  in  calico  printing  and  in  the 
manufacture  of  fire-works  and  friction  matches.  It  is 
chiefly  valuable  as  an  oxidizing  agent. 

Experiment  261. — Melt  some  KN03  in  an  old  flask.  Put  a  basin  of 
H20  under  the  flask.  Pour  powdered  charcoal  into  the  melted  tail 
and  quickly  remove  the  lamp.  A  brilliant  combustion  will  take 
place  and  probably  break  the  flask.  The  C  is  energetically  oxidized 
forming  large  volumes  of  C03 

2S2.  Potassium  Nitrate.  —  Potassium  nitrate 
(nitre,  saltpetre,  KN03)  is  found  as  an  efflorescence  on 
the  soil  in  various  tropical  regions,  especially  in  Bengal. 
It  does  not  extend  into  the  soil  to  a  depth  greater  than 
that  to  which  the  air  can  easily  penetrate.  It  is  extracted 
by  solution  in  water  and  evaporation.  It  is  also  found 
in  many  caverns,  and  is  seldom  wanting  in  a  fruitful  soil. 
It  is  chiefly  used  in  the  preparation  of  nitric  acid  and  the 
manufacture  of  gunpowder.  It  is  a  white,  inodorous 


§  286  POTASSIUM.  243 

solid,  permanent  in   the    air   and  very    soluble    in  hot 
water. 

(a.)  When  animal  or  vegetable  matter  decays  in  the  presence  of  air 
and  in  contact  with  an  alkaline  or  earthy  base,  the  NH3  produced 
is  gradually  oxidized  to  HN03  and  "fixed"  by  the  alkali.  Thus 
the  well-waters  of  most  towns  contain  nitrates,  showing  that  they 
have  been  contaminated  by  sewers,  cess-pools  or  other  causes.  The 
artificial  production  of  KN03  is  regularly  carried  on  in  Sweden, 
Switzerland  and  other  parts  of  continental  Europe. 


283.  B, it  hi u in. — Lithium  (symbol,  Li ;  atomic  iceight,  7  m.c.)  is 
a  rare  metal  and  the  lightest  known  elementary  solid,  its  specific 
gravity  being  0.59.  It  was  first  prepared  in  the  metallic  state  in 
1855.  It  is  closely  allied  to  sodium  and  potassium,  but  is  harder  and 
less  easily  oxidizable  than  they.  It  melts  at  about  180°  C. 


28  J.  Rubidium.  —  Rubidium  (symbol,  Rb  ;  atomic  weight, 
85.2  m.  c.)  is  a  rare  metal  found  only  in  very  minute  quantities.  Its 
specific  gravity  is  1.52.  It  resembles  potassium  so  closely  that  it  can 
not  be  distinguished  from  it  by  the  ordinary  wet  reactions  or  blow- 
pipe tests  or  any  other  means  except  that  most  delicate  of  all  de- 
terminative processes,  spectrum  analysis  (Ph.,  §  638,  &.).  It  was  dis- 
covered by  this  means  in  1861.  It  melts  at  about  58°  C. 


285.  Caesium.—  Csesium  (symbol,  Cs;  atomic  weight,  132. 5  m.c.} 
was  discovered  by  spectrum  analysis  in  1880,  being  the  first  element 
thus  discovered.     It  closely  resembles  potassium  and  rubidium,  with 
which  it  generally  occurs.     The  only  means  of  its  detection  and  re- 
cognition is  spectrum  analysis,  which,  however,  makes  evident  its 
minutest  trace.     It  is  the  most  decidedly  electro-positive  of  all  of 
the  elements.     Its  specific  gravity  is  not  yet  known. 

286.  Ammonium. — Ammonium  is  a  name  given  to 
the  compound  radical,  NH4.    It  acts,  as  do  the  other  mem- 
bers of  this  group,  as  an  alkali,  monad  metal  but  it  has  not 
been  isolated  (§  168). 

(<z.)  The  assuming  of  this  hypothetical  metal  makes  the  analogies 


244  POTASSIUM.  §  286 

between  the  composition  of  the  salts  of  the  "  volatile  alkali  "  and 
the  composition  of  those  of  the  fixed  alkalies  as  evident  as  are  the 
analogies  between  their  properties  ;  e.  g. 

Ammonium  hydrate.        Potassium  hydrate.        Sodium  hydrate. 


287.  Ammonium  Chloride.  —  Ammonium  chlo- 
ride (salammoniac,  NH4C1)  is  found  native  in  certain  vol- 
canic regions  and  is  artificially  prepared  in  large  quantities 
from  the  ammoniacal  liquors  of  gas  works.    It  occurs  in 
commerce  as  tough,  fibrous  masses.    It  is  used  in  medicine, 
in  soldering  to  dissolve  the  metallic  oxides,  in  dyeing,  and 
in  the  laboratory  as  a  convenient  source  of  ammonia  and 
for  other  purposes. 

(a.)  The  ammoniacal  liquor  of  gas  works  is  heated  with  lime  and 
the  gaseous  NH3  thus  evolved  is  passed  through  dilute  HCI  until  it 
is  saturated.  The  solution  is  evaporated  and  the  NH4CI  purified  by 
recrystallization  from  hot  H80  or  by  sublimation. 

Experiment  262.—  Dissolve  6  g.  of  (NH4)N03  in  10  cu.  cm.  of  ice 
cold  H20.  Stir  the  mixture  with  a  thermometer  and  notice  the  re- 
sulting temperature. 

288.  Ammonium  Nitrate.  —  Ammonium  nitrate 
(NH4N03)  is  prepared  by  neutralizing  dilute  nitric  acid 
with  dilute  ammonia  water  or  a  solution  of  ammonium 
carbonate  and  evaporating  the  solution.     It  decomposes 
by  heat  into  water  and  nitrogen  monoxide  (§  79).     It  has 
a  saline  taste,  dissolves  easily  in  half  its  weight  of  water 
with  the  production  of  cold  (Ph.,  §  520). 

Note.  —  Ammonium  salts  are  very  numerous,  inos*t  of  them  being 
prepared  directly  or  indirectly  from  the  ammoniacal  liquors  of  gas 
works.  They  are  generally  soluble  in  water. 


§  288  POTASSIUM.  245 

T(%>  ^'^'tV;J' 

EXERCISES.     ^  / 

1.  The  practical  yield  being  half  the  theoretical,  how  much  potas- 
sium may  be  prepared  from  138  Kg.  of  potassium  carbonate?,/  \M^A 

2.  What  is  the  percentage  composition  of  KCI03  ?  7~  «?^H 

3.  What  is  the  radical  of  potash  ?  ' 

4.  Give  at  least  one  reason  in  favor  of  each  of  the  following  sym- 
bols for  salammoniac  :  NH3HCI  and  NH4CI. 

5.  Complete  the  following  equations':  '     A/J|C*/V 

(a.)  HNCX  +  NH3  = 

WH§S04  +  KHO=/f< 

(c.gHN08  +  PbO  = 

6.  What  is  the  molecular  weight  of  caustic  potash  ? 

7.  I  explode  a  mixture  of  4  I.  of  H  and  5  I.  of  Cl.    (a.)  What  volume 
of  HCI  is  produced  ?    (b.)  Which  gas,  and  how  much  of  it  remains 
uncombined  ? 

8.  (a.)  What  volume  of  N20maybe  formed  by  heating  30j7.,of' 
NH4N03  ?    (b.)  What  will  the  volume  be  at  15°C.  and  740  mm.  '(? 

9.  Assuming  that  H2O  will  absorb  half  its  weight  of  NH8,  calcu- 
late the  amount  of  NH4CI  necessary  to  the  production  of  3  Kg.  of 
NH4HO.  (3,/^f 

10.  What  substances  do  the  following  symbols  represent :  CH4  ; 

C2H5CI  ;  CHCI3  ;  ^2^(5\  0;    H-O-O-H  ? 

11.  (a.)  Write  the  empirical  symbols  and  the  systematic  names  for 
the  following :      aH5  j-  0  and  pu3  j-  0.      (b.)  What  is  the  common 

)  3    / 

name  for  the  former  ? 

12.  What  is  the  object  of  having  the  room  "  warm  "  for  Exp.  254  ? 

13.  Give  the  names  and  graphic  symbols  for  PCI3  and  PCI6. 

-  ,  i 


METALS    OF    THE    ALKALINE    EARTHS. 


CALCIUM:  symbol,  Ca ;  specific  gravity,  1.58;  atomic  weight, 
39,9  m.  c.  ;  quantivalence  2  and  4. 

289.  Calcium.— Calcium  compounds  occur  largely 
diffused  in  nature,  especially  the  carbonate  in  the  forms  of 
calcite,  chalk,  marble,  limestone,  coral,  etc.  They  are 
found  in  all  animal  and  vegetable  bodies.  The  metal  was 
first  obtained  by  Davy  in  1808,  by  the  electrolysis  of  its 
chloride.  Calcium  is  a  light  yellow,  ductile,  malleable 
metal  about  as  hard  as  gold.  It  is  scarcely  oxidizable  in 
dry  air.  easily  oxidizable  in  moist  air,  burns  vividly  with 
a  very  bright  yellow  light  when  heated  to  redness  in  the 

air  and  decom- 
poses water  with 
evolution  of  hy- 
drogen. 

Note. — The  name, 
calcium,  is  from  calx, 
the  Latin  name  for 
lime. 

290.  Calci- 
um Oxides. — 

Calcium  monox- 
ide (lime,  quick- 
lime, CaO)  is  pre- 
pared by  igniting 
FIG.  no.  calcium  carbo- 

nate.    On  the  large  scale,  lime  is  "  burned  "  from  limestone 


§  2QI        METALS    OF    THE    ALKALINE    EARTHS.  24? 

placed  in  a  kiln  of  rude  masonry  often  built  in  the  side  of 
a  hill,  the  process  requiring  several  days.  Lime  is  a  white, 
amorphous  substance  about  three  times  as  heavy  as  water. 
It  is  infusible  in  even  the  oxy-hydrogen  flame  (§  397)  but 
when  so  heated  emits  an  intense  light,  known  as  the  lime 
or  calcium  light  (Exp.  49).  It  is  largely  used  in  making 
mortars  and  cements  and,  in  the  laboratory,  for  drying 
gases  and  liquids  and  for  other  purposes. 

(a.)  In  the  lime-kiln,  a  limestone  arch  is  built  above  the  fire  and 
the  remaining  limestone  placed  upon  this  arch  from  above.  When 
the  CaO  has  been  burned,  the  kiln  is  allowed  to  cool,  the  CaO  is  re- 
moved and  a  new  charge  introduced.  Improved  kilns  also  are  used 
in  which  the  process  is  continuous,  the  charge  being  introduced  from 
above  and  the  CaO  withdrawn  from  below. 

(&.)  Pure  CaO  may  be  prepared  by  igniting  crystallized  calcite  in  a 
crucible  with  a  perforated  bottom,  so  that  the  C02  may  be  swept 
away  as  it  is  evolved. 

(c.)  When  CaO  is  exposed  to  the  air,  it  absorbs  H.»0.and  C02  and 
falls  to  a  powder  known  as  air  slaked  lime. 

(d.)  Calcium  dioxide  (Ca02)  has  been  prepared  by  precipitation 
from  lime  water  with  H202. 

291.  Calcium  Chloride.  —  Calcium  chloride 
(CaCI2)  is  easily  prepared  by  the  action  of  hydrochloric 
acid  upon  marble,  and  evaporation  of  the  solution.  It 
has  a  strong  attraction  for  water,  is  deliquescent  and  is 
used  for  drying  gases. 

(«.)  CaCI2  may  be  crystallized  from  a  saturated  solution.  These 
crystals  (CaCI2,  6H20),  when  mixed  with  snow,  produce  a  tempera- 
ture of— 48°C.  (Ph.,  §  521). 

Experiment  2G3. — Add  a  few  drops  of  H2O  to  a  small  quantity  of 
slaked  CaO  and  rub  it  to  a  paste  between  the  fingers.  Its  action  can 
be  felt  as  it  actually  dissolves  or  destroys  a  little  of  the  skin. 

Experiment  864. — Put  30  g.  of  recently  burned  CaO  upon  a  saucer, 
hold  the  saucer  in  the  palm  of  the  hand  and  pour  20  cu.  cm.  of  H20 


248  METALS    OF    THE    ALKALINE    EARTHS. 

upoii  it.  Notice  the  increase  of  bulk  and  the  rise  of  temperature. 
Thrust  a  friction  match  iiito  the  crumbling  mass.  It  will  be  heated 
to  the  point  of  ignition.  Sprinkle  a  little  gunpowder  upon  the  slak- 
ing lime  ;  perhaps  it  will  take  fire. 

Experiment  265. — Dip  a  piece  of  colored  cambric  or  calico  into  a 
half  ht3r  of  H20  into  which  15  g.  of  chloride  of  lime  have  been 
stirred.  Notice  the  effect  upon  the  color  of  the  cloth.  Then  dip  the 
cloth  into  very  dilute  HCI  or  H2S04.  Notice  the  effect  on  the  color 
of  the  cloth.  Wash  the  cloth  thoroughly  in  H20. 

292.  Calcium  Hydrate. — When  fresh,  well  burned 
lime  is  treated  with  one-third  its  weight  of  water,  the  di- 
rect synthesis  yields  calcium  hydrate  [calcium  hydroxide, 
caustic  lime,  slaked  lime,  Ca(HO)2>  CaH202]  with  the 
evolution  of  great  heat  (Ph.,  §  524,  5).  Calcium  hydrate 
is  a  white,  alkaline,  caustic  powder.  It  dissolves  more 
easily  in  cold  than  in  hot  water,  yielding  an  alkaline, 
feebly  caustic  liquid  called  lime  water.  Lime  water  readily 
absorbs  carbon  dioxide.  Lime  water  containing  solid 
particles  of  calcium  hydrate  in  suspension  is  called  milk 
of  lime  or  cream  of  lime  according  to  the  consistency  of 
the  mixture. 

(a.)  The  power  of  absorbing  C02  and  H2S  leads  to  the  use  of 
CaH202  in  the  purifiers  of  gas  works.  Its  caustic  action  leads  to  its 
use  (as  milk  of  lime)  in  removing  the  hair  from  hides  for  tanning. 
Its  alkaline  properties  fit  it  for  use  in  making  an  insoluble  "  lime 
soap"  for  stearine  candle  manufacture.  Mixed  with  sand  and  H20, 
it  forms  mortar,  which  absorbs  CO2  from  the  air  and  becomes  a  mix- 
ture of  calcium  hydrate  and  carbonate  and  sand  that  firmly  binds 
together  the  bricks  or  stones  between  which  it  has  been  placed. 

(6.)  When  CaH202  is  exposed  to  the  action  of  Cl,  it  forms  "  bleach- 
ing powder"  or  "  chloride  of  lime  "  which  is  made  in  immense  quan- 
tities. This  substance  may  be  considered  a  mixture  of  calcium 
chloride  and  calcium  hypochlorite  (CaCL  +  CaCI202)  or  a  double 
salt,  CaOCI2,  at  once  a  chloride  and  a  hypochlorite  of  calcium, 

ClOf  ^a'  (§11^')  **  *s  sometimes  called  calcium  chloro-hypo- 
chlorite,  and  graphically  symbolized  as  follows  :  CI-Ca-0-CI. 


§  2Q4        METALS    OF    THE    ALKALINE    EARTHS.  249 

Experiment  2GG. — Place  a  little  lime  water  in  a  test  tube  and  pass 
through  it  a  stream  of  C02.  Notice  the  precipitation  of  CaC03  that 
renders  the  liquid  turbid.  Notice  also  that  as  the  passage  of  C02 
into  the  liquid  continues,  the  latter  becomes  clear  again,  the  precipi- 
tate being  dissolved.  Boil  the  clear  liquid  to  expel  some  of  the  ab- 
sorbed CO 2>  and  the  precipitate  again  appears.  Test  the  liquid  at 
each  step  of  the  experiment  with  litmus  paper  to  determine  whether 
it  gives  an  acid  or  an  alkaline  reaction. 

293.  Calcium  Carbonate.  —  Calcium  carbonate 
(CaC03)  occurs  in  many  forms,  both  crystallized  and 
amorphous.  The  shells  of  oysters,  clams  and  other  mol- 
lusks  are  almost  wholly  calcium  carbonate.  .It  forms  the 
greater  part  of  egg  shells  and  is  found  in  bones.  It  is 
found  in  enormous  masses  forming  whole  mountain 
ranges.  It  is  barely  soluble  in  water  but  more  easily 
soluble  in  water  charged  with  carbon  dioxide.  When  cal- 
careous mineral  waters  are  exposed  to  the  air,  they  lose 
part  of  their  carbon  dioxide  and,  consequently,  precipitate 
the  calcium  carbonate  previously  held  in  solution.  Hence, 
the  formation  of  stalactites,  stalagmites,  tufa,  travertine, 
etc.  All  of  the  forms  of  calcium  carbonate  are  easily 
acted  upon  by  even  dilute  acids,  the  action  being  attended 
by  effervescence  due  to  the  escape  of  the  expelled  carbon 
dioxide. 

>  294.  Calcium  Sulphate.  —  Calcium  sulphate 
(CaS04)  is  found  in  nature  as  the  mineral  anhydrite.  The 
hydrated  sulphate  (CaS04,  2H20)  is  gypsum,  which, 
when  in  the  crystalline  form,  is  called  selenite.  By  heat- 
ing gypsum  to  about  120°C.,  it  parts  with  its  water  of  crys- 
tallization forming  plaster  of  Paris.  When  this  plaster  is 
mixed  to  a  paste  with  water,  it  again  unites  with  the  water 
and  becomes  hard  or  "  sets."  Hence,  its  use  as  a  cement 
and  for  making  casts  of  various  objects.  Calcium  sulphate 


250  METALS    OF    THE    ALKALINE    EARTHS.         §  2Q4 

is  sparingly  soluble  in  water.  Water  containing  calcium 
sulphate  or  carbonate  in  solution  is  called  "  hard/'  Ala- 
baster is  a  variety  of  gypsum. 

(a.)  When  soap  (sodium  or  potassium  stearate)  is  added  to  hard 
water,  there  is  a  metathetical  reaction,  resulting  in  the  formation  of 
an  insoluble  calcium  or  "  lime  soap  "  (calcium  stearate),  which  rises 
as  a  scum  upon  the  surface  of  the  liquid.  The  soap  can  not  perform 
its  proper  office  until  it  has  precipitated  the  calcium  salt.  Other 
agents  are  often  used  to  precipitate  the  calcium  compound  and  thus 
"soften"  the  water. 

295.  Calcium  Phosphate.  —  There  are  several 
calcium  phosphates  (§  242),  the  most  important  of  which 
is  bone-phosphate,  Ca3P208.  It  is  the  chief  inorganic 
constituent  of  the  bones  of  animals.  It  is  important  as  a 
source  of  phosphorus,  and  valuable,  when  ground  to  a 
powder,  as  a  fertilizer. 


STRONTIUM:  symbol,  Sr ;  specific  gravity,  2.5  ;  atomic  weight, 
873  m.  c. ;  quantivalence,  2  and  4. 

296.  Strontium. — This  rare  metal  closely  resembles  calcium 
in  appearance  and  properties.  It  has  two  oxides  (SrO  and  Sr02).  It 
chiefly  occurs  in  the  sulphate  (celestine,  SrS04)  and  in  the  carbonate 
(strontianite,  SrC03). 


BARIUM  :  symbol,  Ba  ;  specific  gravity,  4  ;  atomic  weight,  136.8 
m.  c.  ;  quantivalence,  2  and  4. 

297.  Barium. — This  rare  metal  closely  resembles  calcium  in 
appearance  and  properties.  Its  melting  point  appears  to  be  higher 
than  that  of  cast  iron.  It  has  two  oxides  (baryta,  BaO;  and  Ba02), 
occurs  in  nature  as  a  sulphate  (heavy  spar,  BaS04)  and  decomposes 
cold  water. 


§  297     METALS   OF  THE  ALKALINE  EARTHS.          251 
EXERCISES. 

1.  Write  the  reaction  for  the  burning  of  CaO. 

2.  Write  the  reaction  for  the  preparation  of  CaCI^/J^fT 

3.  Write  the  reaction  for  preparing  calcium  hydroxide.^^W^* 

4.  Why  is  the  formula  for  calcium  hypochlorite  CaCI303  instead 
of  CaCIO,  the  formula  for  hypochlorous  acid  being  HCIO  ? 

5.  When  a  current  of  C02  is  passed  through  an  aqueous  solution  of 
Ba02,  hydroxyl  and  BaCO3  are  formed.     Write  the  reaction.^'?  - 

6.  How  much  KN03  and  H2S04  shall  I  need  to  prepare  enough  *•• 
HN03  to  neutralize  5  Kg.  of  chalk?  (!) 

7.  What  is  the  property  that  chiefly  distinguishes  Cl  and  the  ele- 
ments most  like  it  from  K  and  the  elements  most  like  it  V 

8.  What  is  meant  by  the  statement  that  caustic  soda  is  formed 
upon  the  water  type? 

9.  What  are  the  characteristic  properties  of  C  1 

10.  Write  the  empirical,  typical  and  graphic  symbols  for  common 
salt,  caustic  potash,  baryta,  sulphuric  acid,  acetic  acid  and  marsh 
gas. 

11.  (a.)  What  is  the  weight  of  1  I.  of  Ql?     (b.)  Of   HgS?     (c.) 

of  co?   /*  vy,>-;         hf  131  &   }>9$#tf- 

12.  Compare  and  contrast  P  and  As  respecting  their  physical  and 
'chemical  properties. 

13.  Symbolize  the  sulphates,  nitrates,  chlorides,  chlorates,  acetates, 
*&-         bromides  and  bromates  of  Ca,  Ba  and  Sr. 

14.  How  much  of  each  of  Na  ;  NH4  ;  Sr  and  K  is  equivalent  to  one    * 
^JL  atom  of  Ca? 


I        4fc- 

&.  - 


-v- £^K£-//-~ 

*c       •         *  t 


-  // 


H-  « 


METALS    OF    THE    MAGNESIUM    GROUP. 

MAGNESIUM  :  symbol,  Mg  ;  specific  gravity,  1.75  ;  atomic  weight, 
24  m.  c. ;  quantivalence,  2. 

298.  Magnesium.  —  Magnesium  compounds  are 
widely  and  abundantly  distributed  but  the  metal  is  not 
found  free  in  nature.    It  is  prepared  in  considerable  quan- 
tities by  fusing  together  magnesium  chloride  (MgCl2)  and 
sodium,  or  from  the  double  chloride  of  potassium  and  mag- 
nesium, called  carnallite,  a  mineral  found  abundantly  in 
the  Stassfurt  deposits  (§  276).    It  has  a  silver  white  ap- 
pearance, preserves  its  lustre  in  dry  air  and  tarnishes  in 
moist  air.    It  is  readily  acted  upon  by  most  acids  with 
the    evolution  of   hydrogen    and,    as  it  is  perfectly  free 
from  arsenic,  is  often  used,  instead  of  zinc,  in  Marsh's 
test  (§  246).    It  is  found  in  commerce,  usually  in  the  form 
of  ribbon.     This  ribbon,  when  ignited,  burns  with  a  bril- 
liant light  of  high  actinic  (Ph.,  §  651)  power.     The  mag- 
nesium light  has  been  seen  from  a  distance  of  twenty-eight 
miles  at  sea  and  has  been  used  for  photographic  purposes. 

Experiment  267. — Coil  15  cm.  of  Mg  ribbon  around  a  lead  pencil. 
Change  the  pencil  for  a  knitting  needle  or  iron  wire,  hold  the  wire 
horizontal  and  ignite  one  end  of  the  ribbon.  The  coil  of  Mg  will 
burn  to  an  imperfect  coil  of  MgO. 

299.  Magnesium     Oxide.  —  Magnesium    oxide 
(magnesia,  MgO)  is  formed  when  the  metal  is  burned  in 
air.     It  may  be  prepared  by  the  ignition  of  the  magnesium 
salt  of  any  volatile  acid;  e. g.,  the  carbonate,  nitrate  or 


§302       METALS    OF    THE    MAGNESIUM    GROUP.  253 

chloride.  It  is  used  in  medicine  and  for  making  infusible 
crucibles,  as  it  does  not  melt  below  the  temperature  of  the 
oxyhydrogen  flame. 

30O.  Magnesium  Salts.  —  Magnesium  Chloride  (MgCI2)is 
found  in  sea  water,  in  many  saline  springs  and  as  a  constituent  of 
carnallite.  It  is  largely  used  in  dressing  cotton  goods.  Magnesium 
sulphate  (MgS04)  is  found  in  nature  as  kieserite.  The  hydrated 
sait  (MgS04,7H20)  is  called  Epsom  salt,  and  is  found  in  many  mineral 
waters.  It  is  used  as  a  purgative  and  in  dressing  cotton  goods. 
Magnesium  carbonate  (MgC03)  occurs  as  native  magnesite.  A  mix- 
ture of  the  carbonate  and  the  hydrate  (MgH202)  prepared  by  adding 
Na2C03  to  a  solution  of  MgCI2  or  of  Epsom  salt,  is  called  magnesia 


ZINC  :  symbol,  Zn  ;  specific  gravity,  6.9 ;  atomic  weight,  65 
rn.c.;  quantivalence,2. 

301.  Sources  of  Zinc. — Metallic  zinc  is  not  found 
in  nature.    The  carbonate  (smithsonite,  zinc  spar,  ZnC03); 
the  silicate  (calamine,  Zn2Si04);   the  sulphide  (sphalerite, 
blende,  ZnS)  and  the  oxide  (red  zinc  ore,  zincite,  ZnOj  are 
found  native  in  paying  quantities. 

302.  Preparation. — The  zinc  ore  is  first  roasted  and 
thereby  converted  to  an  oxide.     This  oxide  is  then  smelted 
with  half  its  weight  of  coal  and  the  distilled  zinc  vapor 
condensed  and  purified. 

(tf.)  There  are  several  processes  of  smelting  Zn,  including  the  Eng- 
lish, Belgian  and  Silesian.  In  the  English  process,  the  roasted  ore 
and  coal  are  put  into  iron  crucibles  covered  at  the  top  and  having  an 
iron  tube  fitting  into  the  bottom.  The  crucibles  are  heated  in  conical 
furnaces.  The  vaporized  metal  passes  down  the  tube  and  is  col- 
lected in  vessels.  This  process  is  less  economical  than  the  others. 

(6.)  In  tlie  Belgian  process,  fire  clay  cylindrical  retorts,  1  m.  long 
and  20  cm.  in  internal  diameter  are  used.  About  50  of  these  retorts 
are  set  in  one  furnace,  slanting  slightly  from  a  horizontal  direction 
so  that  the  metal  may  run  out.  Each  retort  is  provided  with  a  taper- 
ing neck  and  a  sheet  iron  condenser.  The  smelting  is  completed  in 
eleven  hours,  two  charges  being  worked  per  day. 


254: 


METALS    OF    THE    MAGNESIUM    GROUP.        §  302 


(O   In   the   Silesian   process,    now   generally   adopted,  fire  day 
mufflers,  M,  M,  about  1  m.  long,  are  arranged  side  by  side  on  the 


FIG.  in. 

floor  of  a  reverberatory  furnace.  The  vaporized  Zn  passes  out  by  the 
bent  clay  tube,  A,  and  is  received,  as  it  condenses,  in  a  vessel  placed 
in  the  closed  recess,  0.  Metallic  Zn,  in  the  form  of  fine  dust,  mixed 
with  ZnO,  is  also  obtained.  The  mixture  is  called  zinc  dust  ;  it  is 
a  valuable  reducing  agent. 

(d.)  The  Zn  is  then  remelted,  cast  into  slabs  or  cakes  and  sent  into 
the  market  under  the  name  of 


Experiment  268. — Mix  20  g.  of  zinc  dust  and  40  g.  of  powdered 
KN03.  (If  you  cannot  get  the  zinc  dust,  pulverize  granulated  zinc, 
§  21).  Heat  a  small  Hessian  crucible  to  redness,  remove  it  from  the 
fire  and  place  it  in  the  ventilating  closet  or  where  the  fumes  that 
may  be  formed  will  be  drawn  into  the  chimney.  By  means  of  a 
ladle  with  a  handle  about  1  m.  long,  drop  the  mixed  Zn  and  KNO3 
into  the  red  hot  crucible.  .  The  Zn  will  burn  with  great  energy  at  the 
expense  of  the  0  of  the  KNOS. 

Experiment  269. — Put  a  pinch  of  finely  powdered  blue  indigo  into 
a  test  tube,  add  half  a  teaspoonful  of  zinc  dust  or  fine  Zn  filings  and 
two  teaspoonfuls  of  a  strong  solution  of  NaHO.  Heat  the  mixture. 
The  nascent  H  evolved  changes  the  blue  indigo  (C8H5NO)  to-  white 
indigo  (C8H8 NO). 


§  304        METALS    OF    THE    MAGNESIUM    GROUP.  255 

Experiment  370. — Dip  a  piece  of  \vliite  cloth  into  the  solution  of 
white  indigo.  When  it  is  exposed  to  the  air,  the  reduced  indigo  is 
oxidized  to  the  blue  variety  and  the  cloth  is  permanently  colored. 
The  color  is  "  fast." 

Experiment  271. — Dissolve  10  g.  of  lead  acetate  (sugar  of  lead)  in 
250  cu.  cm.  of  H30  and  add  a  few  drops  of  C2H402. 
In  this  solution,  suspend  a  strip  of  Zn.  The  Zn  and 
Pb  will  change  places,  leaving  a  solution  of  zinc 
acetate  and  a  metallic  "  lead  tree."  The  tree  will 
be  more  beautiful  if  the  ends  of  the  Zn  be  slit  into 
branches  before  immersion.  The  weights  of  the 
dissolved  Zn  and  the  precipitated  Pb  will  be  in  the 

FIG.  112.        ratio  of  their  atomic  weights. 

3O3.  Properties. —Zinc  is  a  bluish  white,  crystal- 
line metal.  It  is  ductile  and  malleable  at  about  130°C.  or 
140PC.,  under  which  circumstances  it  may  be  drawn  into 
wire  or  rolled  into  sheets  or  plates.  At  the  ordinary  tem- 
perature and  at  temperatures  above  200°C.,  it  is  brittle. 
The  commercial  article  is  seldom  pure,  generally  contain- 
ing lead,  iron  and  carbon,  while  traces  of  arsenic  and  an- 
timony are  often  found.  Zinc  dust  is  a  valuable  reducing 
agent.  Zinc  is  readily  acted  upon  by  a  boiling  solution  of 
sodium  and  potassium  hydrates  and  by  most  acids,  with 
the  evolution  of  hydrogen.  (Ph.,  §§  373,  374.)  It  melts 
at  410°C.,  and  distils  at  about  1000°C.  Pure  zinc  is  not 
easily  soluble  in  dilute  sulphuric  acid  while  impure  zinc  is 
thus  soluble  (Ph.,  §  386.)  Zinc  is  not  much  affected  by 
air,  either  dry  or  moist.  It  readily  precipitates  most  metals 
from  solutions  of  their  salts. 

(a.)  Brass  is  an  alloy  of  Zn  and  Cu.  German  silver  is  an  alloy  of 
Zn,  Cu  and  Ni. 

(6.)  Galvanized  iron  is  simply  iron  coated  with  Zn.  The  term  is  a 
gross  misnomer,  as  galvanic  action  is  not  involved  in  the  process. 

304L  Zinc  Compounds.  —  Zinc    oxide   (ZnO)   is 


256  METALS    OF    TBE    MAGNESIUM    GROUP.         §  304 

found  as  an  ore  in  New  Jersey.  Its  color  is  due  to  the 
presence  of  red  oxide  of  manganese.  Zinc  oxide  is  known 
in  commerce  as  zinc  ivliite,  and  is  prepared  on  a  large  scale 
for  use  as  a  paint.  Zinc  chloride  (ZnCI2)  is  formed  by 
dissolving  zinc  in  hydrochloric  acid.  It  is  nsed  for  pre- 
serving timber,  as  a  caustic  in  surgery,  in  cleansing  the 
surfaces  of  metals  for  soldering  and,  very  largely,  for  the 
fraudulent  purpose  of  weighting  cotton  goods.  It  is  solu- 
ble in  alcohol  and  very  deliquescent.  Zinc  sulphate  (white 
vitriol,  ZnS04,  7H20)  is  used  in  medicine,  in  dyeing,  and 
in  galvanic  batteries. 


GLUCINTJM:  symbol,  Gl ;  specific  gravity ,2.1;  atomic  weight, 
9  m.  c. ;  quantivalence,  2. 

305.  Gin  rill  u  m. — This  rare  metal  is  also  known  as  glucinium 
and  as  beryllium  (symbol,  Be).  Its  oxide  is  found  in  the  mineral 
beryl.  By  fusing  its  chloride  with  potassium  or  sodium,  the  metal 
is  formed  as  a  dark  gray  powder  which  acquires  a  metallic  lustre  by 
burnishing.  The  metal  may  be  made  coherent  by  fusing  this  powder 
under  sodium  chloride.  It  has  a  silver  white  color  and  melts  at  a 
lower  temperature  than  silver  does. 


CADMIUM  ;  symbol,  Cd  ;  specific  gravity,  8.6  ;  atomic  weight, 
112  m.  c. ;  molecular  weight,  112  m.  c.  ;  quantivalence,  2. 

3O6.  Cadmium.— This  rare  metal  occurs  in  nature 
associated  with  zinc  ores.  As  it  is  more  volatile  than  zinc, 
its  vapor  comes  over  with  the  first  portions  of  the  zinc  dis- 
tilled. It  forms  compounds  very  similar  to  the  corre- 
sponding zinc  compounds.  It  has  a  tin  white  color,  is 
susceptible  of  a  high  polish  and  gives  a  crackling  sound 
when  bent,  as  tin  does.  As  its  vapor  density  is  56,  we  con- 
clude that  its  molecule  contains  but  a  single  atom. 

(a.)  The  statement  that  the  vapor  density  of  Cd  is  56,  means  that 
the  vapor  is  56  times  as  heavy  as  H.  Consequently  (%  61)  its  mole- 


§  307       METALS    OF    THE    MAGNESIUM    GROUP.  257 

cule  weighs  56  times  as  much  as  the  H  molecule  or  112  m.  c.  But 
this  molecular  weight  is  the  same  as  its  atomic  weight.  Hence,  the 
inference  above  stated. 

3O7.  The  Magnesium  Group.— The  metals  of  this 
group  decompose  water  only  at  a  high  temperature  and 
glucinum,  probably,  not  at  all.  They  are  volatile  and  burn 
with  a  bright  flame  when  heated  in  the  air.  Each  mem- 
ber of  the  group  forms  only  one  oxide  and  one  sulphide. 
' 

EXERCISES. 

1.  (a.)  In  the  preparation  of  Mg  from  magnesium  chloride  and  so- 
dium, what  is  the  other  product  of  the  reaction?    (&.)  How  may  it 
•be  separated  from  the  metal  ?    (c.)  What  is  the  other  product  when 
it  is  prepared  from  carnallite  ? 

2.  How  much  ZnO  can  be  obtained  by  oxydizing  100  g.  of  Zn  ? 

What  weight  of  C0a  is  yielded  by  the  burning  cf  1  I.  of  CH4  ? 

If  150  cu.  cm.  of  0  and  400  cu.  cm.  of  H  are  mixed  and  ex- 
ploded, (a.}  what  volume  of  steam  is  produced  ?  (&.)  Which  gas,  and 
now  much  of  it,  remains  in  excess?  ,  '& 

5.  By  a  series  of  electric  sparks,  I  decompose  100  cu.  cm.  of  NH3, 
add  90  cu.  cm.  of  0  and  explode  the  mixture.    Give  the  name  and 
volume  of  each  of  the  remaining  gases. 

6.  Write  the  name  and  full  graphic  symbol  for 

S-(S02)-(HO)       - 
S-(S08)-(HO)' 

'u-  •>-o-$-0-V-d'~tf-C 


METALS    OF    THE     LEAD     GROUP. 


LEAD:   symbol,  Pb  ;  specific  gravity,  11.37;  atomic  weight, 
206.4  m.  c. ;  quanticalence,  2  (and  4). 

SOS.  Source  of  Lead. — Lead  is  seldom  found  free 
in  nature  but  its  sulphide  (galena,  galenite,  PbS)  is  quite 
abundant  and  is,  by  far,  its  commonest  ore.  The  lead  sul- 
phide is  generally  associated  with  silver  sulphide. 

309.  Preparation. — The  smelting  of  lead  from  its 
ore  is  a  simple  process.     The  ore  is  first  heated  in  an  open 
reverberatory  furnace,  in  which  one  part  of  the  sulphide 
is  oxidized  yielding  lead  oxide  (PbO)  and  sulphur  dioxide 
while  another  part  is  oxidized  to  lead  sulphate.      The 
furnace  is  then  closed  and  heated  to  a  higher  temperature 
when  the  oxide  and  sulphate  just  formed  act  each  upon 
a  part  of  the  still  undecomposed  ore,  yielding  metallic  lead 
and  sulphur  dioxide. 

310.  Properties.— Lead  is  a  metal  so  soft  as  to  be 
easily  cut  with  a  knife  or  indented  with  a  finger  nail  and 
to  leave  a  streak  when  rubbed  upon  paper.     It  has  con- 
siderable malleability  and  little  ductility.     Eepeated  fusion 
renders  it  hard  and  brittle,  probably  by  oxidation.     When 
freshly  cut,  it  has  a  bluish  gray  color  and  a  bright  lustre 
which  is  quickly  dulled  by  oxidation.     It  melts  at  334°C. 
and  may  be  crystallized  by  slowly  cooling  a  large  quantity 
of  the  melted  metal  and  pouring  out  the  still  liquid  por- 


§  313  METALS    OF    THE    LEAD     GROUP.  259 

tion.     It  is  very  slightly  acted  upon  by  cold   sulphuric 
or  hydrochloric  acid ;  its  best  solvent  is  nitric  acid. 

(a.}  Potable  waters  in  general  and  especially  well  waters  contain- 
ing ammoniacal  salts,  often  due  to  decaying  organic  matter,  act  upon 
lead  with  the  formation  of  compounds  that  act  as  cumulative  poisons. 
In  many  cases,  the  use  of  lead  water  pipes  is  very  dangerous  for  this 
reason.  If,  upon  examining  the  inner  surface  of  a  lead  pipe  that  has 
been  thus  used,  it  is  found  to  be  bright  it  may  be  known  that  danger- 
ous soluble  salts  have  been  formed  and  carried  away  with  the  water. 
"  A  word  to  the  wise  is  sufficient." 

(6.)  In  the  presence  of  air  and  moisture,  lead  is  attacked  by  even 
feeble  acids  like  acetic  or  carbonic  acid.  Hence,  the  use  of  cooking 
utensils  that  are  made  of  lead  or  that  contain  lead  even  in  the  form 
of  solder  or  as  an  adulteration  of  otherwise  harmless  substances 
(§  388,  &.)  sometimes  leads  to  the  formation  of  poisonous  lead  com- 
pounds. When  these  are  taken  into  the  system,  they  unite  with  cer- 
tain tissues  of  the  body  and  may  accumulate  until  the  quantity  is 
sufficient  to  produce  poisoning  (§  315). 

311.  Uses.  —  Lead  is  largely  used  for  many  purposes 
on  account  of  its  softness,  pliability,  easy  fusibility  and  its 
comparative  freedom  from  chemical  action  with  water  and 
most  of  the  acids. 

312.  Lead  Oxides,  —  Lead  suboxide  (Pb20)  is  also'  called 
plumbous  oxide.     Lead  monoxide  (PbO)  is  also  called  plumbic  oxide 
but  more  frequently,  litharge.    It  is  prepared  on  the  large  scale  by 
highly  heating  me1! ted  lead  in  a  current  of  air.     It  is  used  in  the 
manufacture  of  glass.     Lead  sesquioxide  (Pb203)  is  considered  to  be 
a  compound  of  the  monoxide  and  dioxide.     Eed  lend  or  minium 
(Pb304)  is  largely  used  as  a  paint  and  in  the  manufacture  of  flint 
glass.     Lead  dioxide  (Pb02)  or  plumbic  peroxide  is  most  easily  pro- 
duced by  treating  red  lead  with  nitric  acid. 

313.  JLeatl  Sulphide.— Lead  sulphide  (PbS)  occurs  native  as 
galenite  or  galena  and  may  be  prepared  artificially  by  passing  hy- 
drogen sulphide  into  any  solution  of  a  lead  sa?t.     The  precipitate 
thus  formed  is  of  a  deep  but  varying  color.     This  color,  together 
with  the  insolubility  of  the  precipitate  is  of  use  in  detecting  the 
presence  of  lead. 


260  METALS    OF    THE    LEAD    GROUP.  §  314 

314.  Some  L.ca<l  Salts.— There  are  two  compounds  of  lead 
and  chlorine  ;  plumbic  chloride   (PbCI2)   and    plumbic    perculoride 
(PbCI4).    Lead  carbonate  (PbC03)  is  formed  as  a  white  precipitate  by 
adding  ammonium  carbonate   to  a  cold  solution  of  lead  acetate. 
White  lead  is  a  compound  of  varying  proportions  of  the  carbonate 
and  hydrate.     When  ground  with  linseed  oil,  it  forms  the  basis  of 
ordinary  white  paint  although  zinc  white  is  used  for  the  same  pur- 
pose.    Lead  acetate  is  a  soluble  salt  with  a  sweet,  astringent  taste, 
whence  its  common  name,  sugar  of  lead.    Like  the  other  soluble 
lead  salts  it  is  intensely  poisonous. 

315.  Lead  Poisoning.— While  metallic  lead  is  not 
poisonous,  all  of  its  soluble  salts  are  so  in  a  very  high  de- 
gree.    Lead  acetate,  given  in  doses  of  from  0.3  g.  to  0. 6  g. 
produces  symptoms  of  acute  lead  poisoning  which  often 
end  fatally.     Small  doses  of  the  oxides  and  carbonates 
frequently  repeated  often  produce  chronic  lead  poisoning 
(§  310,  b).     Painter's  colic  is  a  form  of  chronic  poisoning 
by  lead  carbonate.    Soluble  sulphates,  e.g.,  Epsom  salt. 
are  antidotes  for  lead  poisons. 

316.  Tests.— The  sweet  taste  and  poisonous  character 
of  the  soluble  lead  salts  render  their  detection  a  matter  of 
great  importance. 

(«.)  Any  Pb  compound  when  heated  on  charcoal  in  the  blowpipe 
flame  gives  a  bead  of  malleable  lead.  This  bead  is  readily  soluble 
in  warm  HN03  ;  and  this  acid  solution  yields  a  precipitate  with 
H2S04. 

(&.)  Potable  waters  suspected  of  containing  Pb  compounds  may  be 
tested  by  slightly  acidulating  with  HCl  and  charging  with  H2S.  If 
a  black  precipitate  is  formed,  lead  is  probably  present.  The  proba- 
bility is  sufficient  to  call  for  the  services  of  a  chemical  expert.  If 
lead  salts  are  present  in  not  too  minute  quantities,  the  addition  of 
HCl  will  yield  a  white  crystalline  precipitate  of  PbCI2  which  is  solu- 
ble in  an  excess  of  boiling  H20.  If  the  solution  of  the  lead  salt  be 
tolerably  strong,  the  addition  of  KI  will  generally  yield  a  yellow  pre- 
cipitate of  PbI2,  while  the  addition  of  potassium  chromate  (K2Cr04) 
gives  a  fine  yellow  precipitate  of  lead  chromate  or  chrome  yellow 
(PbCr04). 


§  3l8  METALS    OF    THE    LEAD     GROUP.  261 


THALLIUM:  tymbct,T\;  specific  gravity,  ll.S;  atomic  weight \ 
203.6  m.  c. ;  quantivalence,  1  and  3. 

317.  Thallium. — Thallium  is  a  very  rare  metal,  dis- 
covered in  1861  by  spectrum  analysis,  by  which  means  it 
has  been  found  to  be  widely  but  very  sparingly  distributed. 
It  is  generally  prepared  from  the  "  flue  dust "  that  accumu- 
lates between  the  pyrite  furnace  and  the  leaden  chambers 
in  sulphuric  acid  works.     It  has  a  bluish,  white  tint  and 
a  lead  like  lustre.     It  leaves  a  streak  when  rubbed  on  paper 
and  is  easily  indented  by  a  finger  nail,  being  softer  than 
lead.      It  is  malleable  but  not  ductile.     It  decomposes 
water  at  a  red  heat  and  is  easily  soluble  in  dilute  acids.    Its 
salts  are  poisonous.     It  melts  at  294°  0. 

(a.)  Tl  forms  two  oxides,  the  monoxide  (TlaO)  and  the  trioxide  or 
sesqtiioxide  (TI2O3).  There  are  also  two  corresponding  series  of 
salts,  the  thallious  and  the  thallic. 

(&.)  Tl  has  a  peculiar  position  among  the  metals.  Like  Na  and  K, 
it  replaces  H,  atom  for  atom  ;  it  also  presents  other  analogies  with 
the  metals  of  that  group.  Like  gold,  it  forms  a  trichloride  (TICI3). 
It  also,  as  we  have  seen,  corresponds  closely  to  Pb.  On  account  of 
this  difficulty  of  classification  it  has  been  termed  the  metallic  orni- 
thorhynchus. 

318.  The  Lead  Group.— The  metals  of  this  group 
are  soft ;  they  have  a  high  specific  gravity ;  their  sulphides 
are  black  and  insoluble  in  water ;   their  chlorides  are 
sparingly  soluble. 


METALS    OF    THE    LEAD    GROUP.  §  318 

***** 

EXERCISES. 

1.  (a.)  Write  the  reaction  for  the  formation  of  lead  oxide  in  the  first 
stage  of  lead  smelting.     (&.)  For  the  formation  of  lead  sulphate  in 
the  same  stage. 

2.  (a.)  Express  the  reaction  between  the  lead  oxide  and  galenite 
in  the  second  stage  of  lead  smelting.     (&.)  For  the  reaction  between  e 
lead  sulphate  and  the  ore  in  the  same  stage.  ££fr(  \£$tl-*p$  \  Q.  CV 

3.  Write  the  reaction  for  the  preparation  of  lead  peroxide  from 
red  lead  and  nitric  acid. 

4.  (a.)  What  substance  may  be  represented  by  the  graphic  symbol 

/°\ 

0  =  Pb         .Pb?    (6.)  What  does  this  symbol  show  concerning  the 

^0' 

quantivalence  of  the  lead  atoms  in  the  molecule? 

5.  (a.)  What  substance  is  represented  by  the  symbol 

0— Pb. 
0  =  Pb  O  ?    (&.)  What  does.this  svmbol  indicate  concern- 

\0— Pbx  ^  (  .    . 

ing  the  quantivalence  of  the  lead  atoms? 

6.  What  volume  of  C02  is  produced  by  the  burning  of  lAof  CH4  ?/  f 

7.  What  is  the  volume  of  1  Kg.  of  0  ?  */j!T 

8.  Write  the  water  type  symbol  for  lead  acetate. 

9.  What  is  common  washing  soda?    Baking  soda?    Why  is  the 
latter  better  for  baking  than  the  former  ? 


ay 


METALS    OF    THE    COPPER    GROUP. 


COPPER. 

Symbol,  Cu ;  «pcci/fe  gravity,  8.95  ;  atomic  weight,  63.1  m.  c.  ; 
quantivalence,  2. 

319.  Source. — Copper  was  probably  the  first  metal 
used  by  man  as  it  is  found  native  and  thus  requires  no 
metallurgical  treatment.    Native  copper  is  found  in  large 
masses,  especially  in  the  Lake   Superior  mines,  where  a 
single  mass  weighing  480  tons  was  discovered. 

(a,)  Among  the  more  important  of  the  copper  ores  are  cuprite  or 
red  copper  ore  (Cu30);  malachite  (CuC03  +  CuH202) ;  azurite 
(2CuC03  +  CuH?.02);  chalcocite  or  copper  glance  (Cu2S)  and  chal- 
copyrite  or  copper  pyrites  (CuFeS2),  the  last  being  the  most  im- 
portant. 

320.  Preparation.  —  The  reduction  of  the  oxides 
and  carbonates  is  easily  effected  by  smelting  with  carbon. 
The  sulphides  are  roasted  to  volatilize  some  of  the  con- 
stituents and  to  oxidize  others.    The  roasted  ore  is  then 
fused  with  a  silicate,  whereby  a  slag  containing  most  of 
the  iron  is  formed  and  a  nearly  pure  copper  sulphide  is  ob- 
tained.   This  sulphide  is  then  roasted ;  part  of  the  copper 
is  oxidized  and  combines  with  the  remaining  sulphide, 
yielding  metallic  copper  and  sulphur  dioxide. 


264  METALS    OF    THE    COPPER    GROUP.  §  320 

(a.)  In  the  smelting  process,  some  of  the  oxide  dissolves  in  the 
melted  metal  and  makes  it  so  brittle  as  to  be  unfit  for  use.  It  is 
"toughened"  by  "poling "or  stirring  the  melted  metal  with  the 
trunk  of  a  young  tree,  the  surface  of  the  metal  being  covered  with 
a  thin  layer  of  coal.  Reducing  gases,  such  as  CO  and  various  hydro- 
carbons,  are  evolved  in  large  quantities  from  the  green  wood  and 
sufficiently  reduce  the  oxide.  If  the  metal  is  "  over-poled,"  com- 
pletely reduced  and  thus  made  brittle  again,  it  is  exposed  to  the  air 
for  a  short  time  and  thus  brought  back  to  the  "  tough  pitch  "  once 
more. 

321.  Properties.— Copper  is  a  reddish  metal,  hard, 
very  tenacious  and  highly  malleable  and  ductile.     Except- 
ing silver,  it  is  the  best  known  conductor  of  heat  and 
electricity  (Ph.,  §  539,  I).    It  is  not  much  affected  by  air 
or  by  most  of  the  acids  at  the  ordinary  temperature.    It 
melts  at  about  1200°C. 

(a.)  Cu  is  readily  dissolved  by  dilute  HN03,  yielding  Cu(N03)3  and 
NO  (£  83).  It  is  dissolved  in  hot  H2S04,  yielding  CuS04  and  SO* 
(§  145, «.). 

322.  Uses.— Copper  is  largely  used  for  many  familiar 
purposes.     On  account  of  its  toughness,  it  is  used  in  the 
manufacture  of  tubular  boilers,  for  coating  the  bottoms  of 
ships,  etc.;  on  account  of  its  conductivity,  it  is  employed 
in  ocean  cables  and  for  other  electric  uses.     Brass,  bronze, 
bell-metal  and  other  copper  alloys  are  of  great  technical 
importance  and  are,   perhaps,  used  more   than    copper 
itself. 

Experiment  272. — Hold  a  bright  Cu  coin  obliquely  in  the  small 
flame  of  a  gas  or  alcohol  lamp.  Move  it  to  and  fro  and  notice  the 
beautiful  play  of  iridescent  colors.  Cool  the  coin  in  H20  and  notice 
its  coaling  of  red  oxide.  Heat  the  coin  again,  holding  it  in  the  hot, 
oxidizing  part  of  the  flame,  just  above  the  luminous  cone  and  notice 
that  it  becomes  coated  with  a  black  oxide.  Quickly  cool  the  coin  in 
H20  and  notice  that  the  black  coat  scales  off  and  reveals  the  redcoat 
beneath. 


§  324  METALS    OF    THE    COPPER    GROUP.  265 

Experiment  273.—  Place  a  small  quantity  of  dry  Cu(NOa)2  upon  a 
piece  of  porcelain  and  heat  it  until  red  fumes  are  no  longer  given  off. 
A  black  copper  oxide  will  be  left  upon  the  porcelain. 

323.  Copper  Oxides. — Copper  tetrantoxide  or  quadrant  ox- 
ide (Cu40)  is  an  olive  green  powder  that  absorbs  oxygen  when  ox- 
posed  to  the  air.    Coppar  suboxide,  (copper  hemioxide,  cuprous  oxide, 
red  oxide  of  copper  or  ruby  copper,  Cu20)  is  found  native  and  pro- 
pared  artificially.     It  is  used  in  coloring  glass.     Copper  monoxide 
(cupric  oxide,  black  oxide   of  copper,  CuO)   may  be  prepared  by 
heating  the  metal  in  a  current  of  air,  or  by  igniting  the  carbonate, 
hydrate  or  nitrate.     It  is  used  in  coloring  glass  green.     Copper  diox- 
ide (cupric  peroxide,  Cu02)  is  a  yellowish  brown  powder  that  de- 
composes easily  into  CuO  and  0  (see  §  341,  a). 

Experiment  274'— Saturate  a-  strip  of  filter  paper  with  a  solution 
of  Cu(N03)2  to  within  an  inch  of  the  end.  Hold  the  strip,  dry  end 
downward,  over  a  hot  stove.  The  paper  will  ignite  at  the  lower  edge 
of  the  saturated  part  of  the  paper. 

Experiment  275. — Powder  some  blue  vitriol  and  heat  it  upon  a 
pieco  of  porcelain  ;  as  it  loses  its  H20,  the  light  blue  powder  will 
turn  white.  A  drop  of  H20  upon  the  anhydrous  powder  will  restore 
the  color. 

324.  Some    Copper    Salts.  —  Copper    nitrate 
(CuN206)  is  prepared  by  treating  copper  with  nitric  acid 
and  evaporating  the  solution.     On  crystallizing  from  its 
solution,  it  absorbs  three  molecules  of  water  (CuN206, 
3H20).    It  is  easily  decomposable  and,  therefore,  has  strong 
oxidizing  properties.     Copper  sulphate  (CuS04)  is  formed 
by  dissolving  copper  in  hot  sulphuric  acid  or  the  oxide  in 
dilute  sulphuric  acid.    It  is  also  prepared  from  the  ores  and, 
as  a  secondary  product,  in  silver  refining.     It  is  generally 
found  as  hydrated  crystals  (CuS04,  5H20)  known  as  Hue 
vitriol,  which  is  largely  used  in  the  arts.    The  color  of  blue 
vitriol  depends  upon  the  presence  of  its  water  of  crystal- 
lization.   Two  native  carbonates,  malachite  and  azurife, 
have  been  mentioned.     Some  varieties  of  malachite  are 
susceptible  of  a  high  polish  and  are   highly  prized  for 


266  METALS    OF    THE    COPPER     GROUP.  §  324 

jewels  and  other  ornamental  articles.  Copper  acetate  is 
called  verdigris,  although  the  term  is  sometimes  used  to 
designate  the  green  carbonate  that  forms  on  the  exposure 
of  copper  to  moist  air.  Paris  green  is  a  copper  arsenite 
It  is  used  in  green  paints  and  in  modern  potato  culture. 

Note. — The  soluble  copper  salts  are  active  poisons.  Such  salts  are 
formed  in  copper  cooking  utensils  that  are  not  kept  bright.  Acid 
solutions  (e.  g.,  vinegar)  form  poisonous  compounds  with  brass  OP 
copper  utensils  even  when  they  are  kept  perfectly  clean.  Some  per- 
sons prefer  to  pickle  cucumbers  in  brass  or  copper  kettles  because 
they  take  a  more  brilliant  color.  This  added  color  is  due  te  the 
formation  of  poisonous  verdigris.  ,3  .$&  \\ifi  <7t 'f/ 

EXERCISES. 

1.  Read  the  following^ equation  by  unit  volumes  : 

CH4  +20.  =  CO,  +2H20. 

2.  What  weight  of  Cu  is  necessary  to  prepare  1  /.  of  NO  at  0°C.    „ 
and760w/w.  ?  //£JV  £  *. 

3.  The  combustion  of  1  1.  of  CH4  requires  what  volume  of  0? 

4.  What  volume  of  CH4  is  needed  toyiejcj  1  cu.  m.  of  .steam  in  its 
combustion?  .      . 

5.  How  many  cu.  cm.  of  S02  (at  20°C  and  740  mm.,  PLtfS  41 
can  be  obtained  by  the  action  of  Cu  upon  20 g.  of  H2S04 ?  7jK'$ 

6.  What  is  the  symbol  and  nomo  of  a  substance  the  vapor'creus 
of  which  is  30  and  the  percentage  composition  of^wjiicl 
lows:  C,40#;  H,  6.67$  ;  0,  58.3S#  ?«fefcte 

7.  Compare  the  cost  of  making  HNO.,  from  KN03  and  from 
when  the  cost  of  KN03  is  44  cents  per  Kg.,  that  of  NaN03  is  33  cents 
per  Kg.  and  that  of  H3S04  is  11  cents  per  Kg. 

8.  Required  the  volume  of  gases  in  an  eudiometer  after  the  explo- 
sion of  50  cu.  cm.  of  H  with  75  cu.  cm.  of  0  at  150°C.  and  760  mm. 

9.  Assuming  Cu  to  be  a  dyad,  write  graphic  symbols  for  Cu40, 
CuoO,  CuO,  CuOo  and  Cu8CI8.  J>  <? 

r 

iU'   ?£',/*  te*    «^ 

I    ^**  , . -i 


,  c>   •       V 


f  w 


§327  SILVER. 

tW*        '-v- 


SILVER. 


Symbol,  Ag ;  specie  gravity,  10.5  ;  atomic  weight,  107.6  m.  c.  ; 

guantivalence,  1  and  3. 

325.  Source.  —  Silver  is  a  widely  diffused  and  some- 
what abundant  element  and  lias  been  known  from  the 
earliest  times.     It  is  found  native,  sometimes  in  masses 
weighing  several  hundred  pounds  and  often  alloyed  with 
copper,  mercury  and  gold.     It  more  commonly  is  found  as 
a  sulphide,  mixed  with  other  metallic  sulphides.    Its  most 
abundant  source  is  argentiferous  galena  although  the  car- 
bonates have  been    found  in  richly  paying    quantities, 
especially  in  the  Leadville  (Colorado)  mining  region. 

326.  Preparation.  —  The  processes  of  preparing  metallic 
silver  from  its  ores  are  numerous  and  widely  different,  depending 
largely,  in  any  given  case,  upon  the  nature  of  the  ore,  the  position 
of  the  mine,  the  price  of  labor,  fuel,  etc. 

327.  Properties.  —  Silver  is  a   beautiful,  brilliant 
white  metal,  harder  than  gold,  softer  than  copper,  exceed- 
ingly malleable  and  ductile  and  the  best  known  conductor 
of  heat  and  electricity.     It  melts  at  1040°C.  and  then  ab- 
sorbs 22  times  its  volume  of  oxygen.     When  the  melted 
silver  cools  quickly,  the  oxygen  escaping  from  the  interior 
of  the  mass  breaks  through  the  hardening  crust  driving 
out  some  of  the  molten  metal  and  giving  the  phenomenon 
known  as  "spitting"  of  silver.     The  metal  is  unaltered  in 
the  air  and  resists  the  action  of  hydrochloric  and  cold  sul- 
phuric acid  but  dissolves  readily  in  nitric  acid. 

{a.)  Ag  is  so  malleable  that  it  may  be  formed  into  leaves  so  thin 


268  SILVER.  §327 

that  4000  measure  only  1  mm.  in  thickness ;  so  ductile  that  1  g.  of  it 
may  make  1800  m.  of  wire  and  so  tenacious  that  a  wire  2  mm.  thick 
will  sustain  a  weight  of  more  than  80  Kg. 

(b.)  Ag  unites  slowly  with  the  halogen  elements  and  more  readily 
with  S  and  P.  The  tarnishing  of  Ag  is  generally  due  to  the  formation 
of  a  silver  sulphide  by  the  action  of  H2S  present  in  the  atmosphere. 

328.  Uses. — Owing  to  its  susceptibility  of  high  polish, 
its  permanency  and  other  properties,  silver  is  much  used 
for  jewelry,  plate  and  coin.     Owing  to  its  softness,  it  is 
generally  hardened  with  copper.     American   and  French 
coin  contain  ten  per  cent,  and  English  coin  7.5  per  cent,  of 
copper.     It  is  used  for  chemical  utensils  as  it  is  not  acted 
upon  by  the  fused  hydrates  of  the  alkali  metals  as  glass 
and  platinum  are. 

329.  Oxides.— There  are  three  oxides  of  silver  ;  silver  tetrant- 
oxide  or  argentous  oxide  (Ag40) ;  silver  hemioxide  or  silver  oxide 
(Ag20)  and  silver  peroxide  or  dioxide  (Ag202).    When  silver  oxide 
(Ag30)  is  digested  with  ammonia,  it  forms  a  very  explosive,  black 
powder,  known  as  fulminating  silver.    Its  composition  has  not  yet 
been  satisfactorily  determined. 

Experiment  276.—  Fill  three  test  tubes  one-third  full  of  H,0  and 
pour  into  each  a  few  drops  of  a  strong  solution  of  AgN03.  Add  2  or  3 
cu.  cm.  of  a  solution  of  NaCI  to  the  contents  of  the  first  tube  and 
shake  it  vigorously,  AgCI  will  be  precipitated  as  a  dense,  white  curdy 
mass.  Add  2  or  3  cu.  cm.  of  a  solution  of  KBr  to  the  contents  of  the 
second  tube  and  shake  as  before;  a  yellowish  precipitate  of  AgBr  will 
be  thrown  down.  Add  1  or  2  cu.  cm.  of  a  solution  of  KI  to  the  con- 
tents of  the  third  tube  and  shake  as  before  ;  yellowish,  flocculent 
Agl  will  be  formed. 

Experiment  277.— Try  to  dissolve  one-third  of  each  of  these  pre- 
cipitates separately  in  HNO3.  They  will  not  thus  dissolve. 

Experiment  218. — Treat  a  second  third  of  each  precipitate  with 
(NH4)HO.  Determine  which  dissolves  most  easily  and  which  least 
easily. 

Experiment  279.— Treat  the  last  third  of  each  precipitate  with  a 
strong  solution  of  sodium  thiosulphate  (§  158,  &).  Each  of  the  halo- 
gen salts  is  quickly  dissolved. 


§  332  SILVER.  269 

Experiment  280. — Precipitate  more  AgCI  from  a  solution  of  AgN03 
by  HCI  or  a  solution  of  NaCI.  Filter  the  solution  and  wash  the  pre- 
cipitate retained  upon  the  filter  thoroughly  with  H20.  Open  the 
filter,  spread  the  curdy  AgCI  evenly  over  it  and  expose  it  to  the  direct 
rays  of  the  sun.  (Ph.,  §  651.)  The  white  precipitate  quickly 
changes  to  violet,  the  color  deepening  with  continued  exposure. 

Note. — The  last  five  experiments  illustrate  the  principal  processes 
of  photography. 

330.  The  Silver  Haloids.— Silver  chloride  (AgCI) 
is  found  native  in  semi- transparent  masses,   called  horn 
silver.    It  may  be  prepared  by  precipitation  from  a  solution 
of  any  silver  salt  by  a  solution  of  hydrochloric  acid  or  any 
other  chloride.     It  is  insoluble  in  water  and  acids  but 
easily  soluble  in  ammonia  water.     Silver  iodide  or  bromide 
is  precipitated  from  a  similar  solution  by  a  solution  of  an 
iodide  or  bromide.     These  compounds  are  much  used  in 
photography. 

331.  Silver    Sulphide    and    Cyanide.— Silver 
sulphide  (Ag2S)  is  an  important  silver  ore  and  is  formed 
artificially  by  the  action  of  sulphur  or  hydrogen  sulphide 
upon  the  metal.     Silver  cyanide  (AgCN)  is  a  white  curdy 
precipitate,  insoluble  in  dilute  nitric  acid  but  soluble  in 
ammonia  water  or  in  solutions  of  the  cyanides  of  the  alkali 
or  alkaline  earth   metals.     It  is  used  in  electro-plating 
(Ph.,  §  399,  a). 

(a.)  When  a  silver  spoon  is  left  for  a  time  in  an  egg  or  in  mustard 
it  becomes  blackened  by  the  formation  of  silver  sulphide.  Hence, 
silver  egg-spoons  are  often  gilded. 

332.  Silver  Nitrate.  —  Silver  nitrate   (AgN03)  is 
prepared  on  a  large  scale  by  dissolving  silver  in  dilute  nitric 
acid  and  evaporating  to  crystallization.      It  is  found  in 
commerce  in  crystals.     When  fused  and  cast  into  sticks,  it 
is  called  lunar  caustic.     In  this  form,  it  is  used  in  surgery, 


270  SILVER.  §  332 

acting  as  a  powerful  cautery.  Pure  silver  nitrate  is  not 
altered  by  exposure  to  sunlight,  but  when  in  contact  with 
organic  substances  it  blackens,  forming  insoluble  com- 
pounds of  great  stability.  It  is,  consequently,  used  in 
making  indelible  inks  and  hair  dyes.  It  is  also  used  in 
medicine  and  in  photography.  Like  all  of  the  other  solu- 
ble silver  salts,  it  is  poisonous. 

333.  Other  §ilver  Salt§.—  Silver  sulphate  (Ag2S04);  silver 
phosphate  (Ag3P04)  and  silver  carbonate  (Ag8C03)  are  among  the 
many  important  silver  salts. 

iWiWMwUb 

EXERCISES. 

1.  Why  do  silver  coins  become  blackened  when  carried  in  the 
pocket  with  common  friction  matches  ? 

2.  564  Kg.  of  lead  sulphife  will  yield  how  much  Fb  ? 

3.  At  a  very  high  temperature,  AgoO  may  be  decomposed  much  as2^4»£J 
the  HgO  was  in  Exp.  56.     Write  the  reaction  in  molecular  symbols. 

4.  What  action  have  the  alkalies  upon  Ag  ?  />  i  {    ic&'«^- 

5.  If  recently  precipitated  and  moist  AgC  I  be  placed  upon  a  sheet 
of  Zn,  a  dark  color  will  soon  appear  at  the  edge  of  the  salt.     The 
chloride  will  soon  be  converted  into  a  dark  gray  powder  of  finely 
divided  Ag.    Explain.  0  4  5  d  '  t"**^         ^   "'£  * 

6.  The  change  mentioned  in  Exercise  5^  will  be  much  more  rapid 
if  the  AgCI  be  moistened  with  HCI.     Why? 

7.  When  AgCI  is  fused  with  an  alkaline  hydrate,  the  chloride  is 
reduced  to  a  metal,  a  non  combustible  gas  is  set  free  and  an  alkaline 
chloride  is  formed.    What  is  the  gas? 

S.  If  a  silver  dime  be  dissolved  in  HNO$,  the  solution  will  be 
blue.  A  solution  of  AgM03  is  colorless.  Whence  the  blue 

<-  °f  ° 


10.  (a.}  How  many  cu.  cm.  of  VI   may  be  obtainecf  firom  1  1.  of 
NH3  ?    (&.)  Of  N  ?    (c.)  How  may  the  elementary  grases  be  obtained 
from  the  compound  ?    (d.)  How  may  the  eudiometer  be  used  to  free 

.  the  N  from  the  H  ? 

11.  If  HCI  be  used  instead  of  cream  of  tartar  with  HNaC08, 
what  residue  would  remain  in  the  biscuit 

'** 

• 


§  337  MERCURY.  271 


ME  RCU  RY. 

Symbol,  Hg  ;  specific  gravity,  13.6  •  atomic  weight,  200  m.  c. ; 
molecular  weight,  200  m.  c  ;  quant ivalence,  2. 

334.  Source.  —  Mercury,   or  quicksilver,  is  found 
native  in  small  quantities  but  chiefly  as  a  sulphide  (HgS) 
called  cinnabar.    The  best  known  deposits  of  cinnabar  are 
at  Idria  in  Austria,  Almaden  in  Spain,  and  New  Almaden 
in  California.     Mercury  is  also  brought  from  China  and 
Japan. 

335.  Preparation.  —  The   sulphide   is   generally 
mixed  with  quicklime  or  iron  turnings  and  distilled.    The 
sulphur  unites  with  the  lime  or  iron  and  the  mercury 
vapor  is  condensed  by  being  brought  into  contact  with 

water. 

336.  Properties. — Mercury  is  a  silver  white  metal, 
liquid  at  the  ordinary  temperature.    It  vaporizes  slowly  at 
ordinary  temperatures,  boils  at  about  357°C.  and  freezes  at 
—39. 4°C.,  becoming  a  ductile,  malleable,  white  solid  which 
can  be  cut  with  a  knife.     The  liquid  is  scarcely  affected 
by  exposure  to  the  air  but,  when  heated  for  a  long  time  in 
the  air,  it  oxidizes.     It  is  soluble  in  strong,  boiling  sul- 
phuric acid  but  its  best  solvent  is  nitric  acid. 

(a.)  The  vapor  density  of  Hg  is  100.    We,  consequently,  conclude 
that  the  molecule  of  this  element  contains  but  a  single  atom  (§  806,  a). 

337.  Uses. — Mercury  is  largely  used  in  the  construc- 
tion of  thermometers,  barometers  and  other  physical  and 
chemical  apparatus,  for  the  collection  of  gases  that  are 


272  MERCURY,   ETC.  §  337 

soluble  in  water,  for  the  preparation  of  mirrors,  for  the  ex- 
traction of  gold  and  silver  from  their  ores,  and  for  the 
preparation  of  various  mercurial  compounds. 

Expcrimen^  SSL—  Prepare  an  amalgam  by  adding  bits  of  Na  to  Hg 
slightly  warmed  in  an  evaporating  dish. 

338.  Amalgams, — Compounds  or  mixtures  of  the 
metals  with    mercury  are  called  amalgams.      They  are. 
generally  formed  by  the  direct  union  of  the  two  metals. 
Many  of  these  amalgams,  or  mercury  alloys,  are  largely 
used  in  the  arts.     Tin  amalgam  is  used  in   "  silvering " 
mirrors  ;  cadmium  amalgam,  which  gradually  hardens,  has 
been  used  for  filling  teeth ;  zinc  and  tin  amalgam  is  used 
for  coating  the  rubbers  of  electric  machines  (Ph.,  §§  322, 
345). 

339.  Mercury  Oxides. — Mercury  forms  two  oxides, 
mercurous  oxide    (suboxide  of    mercury,  gray   oxide   of 
mercury,  Hg20)  and  mercuric  oxide  (red  oxide  of  mercury, 
red  precipitate,  HgO).     The  latter  is  a  powerful  poison. 
It  is  prepared  by  heating  mercury  for  a  long  time  in  air  or, 
on  the  large  scale,  by  heating  an  intimate  mixture  of  mer- 
cury and  mercuric  nitrate.     It  decomposes,  at  a  red  heat, 
into  its  elementary  constituents  (Exp.  56). 

340.  Mercury  Sulphide. — This  compound  (HgS)  is  largely 
found  native  as  cinnabar.     When  prepared  artificially,  it  is  called 
vermillion.     It  is  of  a  brilliant  red  color  and  is  used  as  an  oil  and 
water-color  paint,  in  lithographers'  and  printers'  inks  and  in  coloring 
sealing-wax. 

341.  Mercury  Salts. — Mercury  forms  two  series  of 
salts,  corresponding  to  the  two  oxides,  viz.,  the  mercurous 
salts  and  the  mercuric  salts.     The  members  of  the  two 
series  are  widely  different  in  their  properties.     The  mer* 


§343  MERCURY,  ETC.  273 

curie  compounds  are  more  powerfully  poisonous  than  are 
the  mercurous. 

(a.)  Mercury  is  generally  considered  a  dyad,  even  in  the  mercurous 
compounds.  In  such  cases,  the  quantivalence  is  explained  by  assum- 
ing that  the  double  atom  (Hg.,)"  partly  saturates  itself  as  is  shown 

Hg-CI 
by  the  graphic  symbol,  |  .    A  similar  explanation  may  be  made 

Hg— Cl 
concerning  the  quantivalence  of  Cu. 

(6.)  Mercury  may  be  detected  in  almost  any  soluble  mercurous  or 
mercuric  salt  by  placing  a  piece  of  clean  Cu  into  a  solution  of  the  salt. 

343.  Mercurous  Salts. — The  most  important  mer- 
curous salt  is  mercurous  chloride  (calomel,  Hg2CI2).  It 
is  tasteless,  odorless  and  insoluble  in  water  and  is,  even 
now.  largely  used  in  medicine.  It  is  commonly  prepared 
by  sublimation  from  an  intimate  mixture  of  mercury  and 
mercuric  chloride. 

(a.)  Mercurous  nitrate  [Hgo(N03)2]  is  formed  by  the  action  of  cold, 
dilute  HN03  on  Hg.  Mercurous  sulphate  (Hg2S04)  is  formed  by 
heating  concentrated  H2S04  with  an  excess  of  Hg  or  by  precipitat- 
ing Hg3(N03)2  with  H2S04. 

(&•)  Hg2Br2  may  be  precipitated  by  adding  HBror  KBr  to  a  solution 
of  Hg2(N03)2.  Similarly,  Hg2I2  may  be  precipitated  by  adding  KI  to 
a  solution  of  Hg2(N03)2.  It  is  also  formed  when  iodine  is  rubbed  with 
the  right  proportion  of  Hg,  a  small  quantity  of  C2H60  being  added. 
It  is  a  green  powder  and  gradually  decomposes  into  HgI2  and  Hg. 

Experiment  282.— Place  a  drop  of  a  solution  of  Hg2(N08)2  or  of 
corrosive  sublimate  upon  a  clean  copper  coin.  Rub  the  drop  over  the 
coin  and  Hg  will  be  deposited  upon  the  Cu. 

343.  Mercuric  Salts. — Mercuric  chloride  (corro- 
sive sublimate,  HgCb)  is  a  powerful  poison.  It  coagulates 
albumen,  forming  an  insoluble  compound,  in  consequence 
of  which  the  white  of  eggs  (§  223)  furnishes  the  best  an- 
tidote in  case  of  poisoning  by  this  salt.  It  unites  with 
many  other  organic  substances  to  form  insoluble,  stable 


274  MERCURF,   ETC.  §  343 

compounds  and  is  used  in  preserving  animal  and  vegetable 
tissues  from  decay.  It  is  somewhat  soluble  in  cold  water 
and  easily  soluble  in  hot  water.  It  is  prepared  by  sublim- 
ing a  mixture  of  mercuric  sulphate  and  sodium  chloride. 

(a.)  Botanical  and  zoological  specimens  are  preserved  from  decay 
and  from  the  attacks  of  insects  by  brushing  over  them  a  solution  of 
HgCI2  in  C2H60. 

(&.)  Mercuric  nitrate  [Hg( NO 3) 2]  is  prepared  by  boiling  Hgin  HN03 
until  a  portion  of  the  liquid  no  longer  gives  a  precipitate  with  NaCI. 
Mercuric  sulphate  (HgS04)  is  prepared  by  heating  Hg  with  at  least 
Vs  times  its  weight  of  H2S04.  It  is  decomposed  by  heat  into 
Hg3S04,  S02,  O  and  Hg. 

(c.)  Hg  combines  directly  with  Br,  forming  HgBr2  and  evolving 
heat.  When  Hg  is  rubbed  in  a  mortar  with  I  and  a  small  quantity 
of  CoH60,  it  forms  HgI2  and  evolves  heat.  It  may  be  precipitated 
by  adding  KI  to  a  solution  of  HgCL.  It  is  a,  scarlet  powder.  (See 

E5,,8.)     v/9r.*f./.il».*}m 


.? 


j 

1.  An  old  process  of  preparing  Hg3CI2  was  to  sublime  a  mixture 
that  gave  this  reaction  :  HgS04  +  Hg  +  2NaCI  =  Na2S04  +Hg2CI2. 
(a.)    Write  this  equation  in  full  molecular  symbols.      (&.)    What 
weight  of  metallic  Hg  is  needed  thus  to  combine  with  1  Kg.  of  NaC!  ? 

2.  Is  Hg(CN)2  a  mercurous  or  a  mercuric  compound?    What  is  its 
name  ? 

3.  Is  cinnabar  a  mercurous  or  a  mercuric  compound  ? 

4.  Zinc  nitrate  and  potassium  carbonate  react  as  follows  : 

Zn(N03)2  +  K2C03  =  ZnC03  +  2KN03. 
ow  much  Zn(N03)2  is  required  to  give  103.17  g.  of  ZnC03  ? 

5.  How  much  ZnC03  may  be  obtained  from  156  g.  of  Zn(N03)2  ? 
How  much  KoC03  is  needed  to  decompose  75  g.  of  Zn(N 

7.  Wliat  quantity  of  KN03  will  result?  f 

8.  How  much  K2C03  must  be  used  to  obtain  54  g.  of  ZnC  _ 

9.  How  much  KN03  will  be  produced?/^£^f  /  Mfaft+j 

10.  It  is  said  that  1  sq.  m.  of  leaf  in  sunlight  will  decompose  1 

of  CO 2  per  hour,     (a.)  What  weight  of  C  will  be  assimilated  in  an 
hour  by  1,000,000  trees,  each  of  which  has  100,000  leaves,  each  leaf 
measuring  25  sq.  cm.?    (&.)  What  will  be  the  volume  of  the  carbon 
assimilated,  assuming  that  its  specific  gravity  is  1 
*4 


i  leaf 
arbon 


• . 


\i 

METALS    OF    THE    ALUMINUM    AND    CERIUM 
GROUPS. 


ALUMINUM:  symbol,  Al ;  specific  gravity,  Z. 6  ;  atomic  weight, 
27.3  m.  c,;  quantivalence  of  the  double  atom  (AI2),  6. 

344.  Source.  —  Aluminum   (or  aluminium)   ranks 
third  among  the  elements  and  first  among  the  metals  in 
quantity  and  extent  of  distribution.      It  is  not  found 
native;  its  oxide  is  found   in  the  minerals  emery  and 
corundum,  among  the  purer  varieties  of  which  are  the 
ruby  and  the  sapphire  ;  its  fluoride,  in  cryolite;  its  silicates, 
in  the  feldspars  and  micas,  the  disintegration  of  which, 
by  weathering,  gives  rise  to  the  several  kinds  of  clay.     It 
is  also  found  in  the  topaz,  emerald  and  garnet.    It  consti- 
tutes about  one-twelfth  of  the  earth's  crust,  and  is  contained 
in  all  fertile  soils  but  is  not  taken  up  by  any  plants  except 
a  few  cryptogams. 

345.  Preparation.  —  Notwithstanding  the  abundance  of 
aluminum  compounds,  no  cheap  method  of  preparing  the  metal  has 
yet  been  found.     It  is  generally  prepared  by  fusing  together,  in  a 
reverberatory  furnace,  100  Kg.  of  an  artificial  double  chloride  of 
aluminum  and  sodium  with  35  Kg.  of  sodium,  adding  40  Kg.  of  cry- 
olite to  act  as  a  flux. 

346.  Properties. — Aluminum  is  a  remarkably  light 
and  sonorous  metal.     It  is  of  a  bluish  white  color  and 
susceptible  of  a  bright  polish.     It  .is  tenacious  and  very 
malleable  and  ductile.    It  is  best  worked  at  a  temperature 
of  from  100°C.  to  150°C.     It  does  not  readily  oxidize  in 
air,  is  insoluble  in  nitric  acid  and  is  not  easily  soluble  in 


276  ALUMINUM,    ETC.  §  346 

sulphuric  acid.  Its  best  solvent  is  hydrochloric  acid  al- 
though it  dissolves  easily  in  boiling  solutions  of  the  alkali 
hydrates. 

347.  Uses.— The  lightness,  lustre,  strength,  unalter- 
ability  in  air  and  hydrogen  sulphide,  ease  of  working, 
sonorous  and  non-poisonous  qualities  of  aluminum  would 
lead  to  an  extensive  use  of  the  metal  were  it  not  for  its 
high  price.  It  is  used  chiefly  in  making  delicate  balances, 
light  weights,  opera  glasses  and  other  instruments  calling 
especially  for  lightness  and  moderate  strength.  Aluminum 
bronze  (90  per  cent.  Cu  +  10  per  cent.  A!)  is  very  hard  and 
malleable,  yields  fine  castings,  lias  the  tenacity  of  steel,  the 
color  of  gold  and  takes  a  high  polish. 

3  18,  Aluminum  O\icle.— Aluminum  oxide  (alumina,  AI203) 
occurs  native  in  corundum,  ruby,  sapphire,  etc.  Its  crystals  are 
second  in  hardness  only  to  the  diamond.  An  impure,  granular 
variety  is  called  emery. 

349.  Other  Aluminum  Compounds  —  The  most  im- 
portant of  the  aluminum  compounds  are  the  silicates,  some  of  which 
have  been  mentioned.  Common  alum  is  a  double  sulphate  of  alu- 
minum and  potassium  [AI2(S04)t,  +  K2S04  +  24H20].  Ammonium 
alum,  now  becoming  common,  differs  in  composition  by  having  am- 
monium sulphate  [(NH4)3S04]  in  place  of  the  potassium  sulphate. 
Cryolite  is  a  double  fluoride  of  aluminum  and  sodium  (AI2F6  + 
6NaF).  A  deposit  80  feet  thick  and  300  feet  long  is  known  on  the 
west  coast  of  Greenland. 


INDIUM:    symbol.  In;  specific  gravity,   7.4 ;  atomic  weight, 
1134  m.  c. 

35O.  Indium. — Indium  is  a  rare  metal  discovered  in 
blende  by  means  of  the  spectroscope  in  the  year  18C3.  It 
is  white,  non-crystalline,  easily  malleable  and  softer  than 
lead.  It  dissolves  slowly  in  hydrochloric  or  dilute  sul- 
phuric acid  but  easily  in  nitric  acid. 


§  353  GALLIUM,   ETC.  277 


GALLIUM:  symbol,  Ga;  specif c  gravity,  5.9;  atomic  iceijht, 
69.8  m.  c. 

351.  Gallium. — Gallium  is  a  rare  metal,  discovered 
in  blende  by  means  of  the  spectroscope  in  the  year  1875. 
It  is  bluish  white,  tough,  may  be  cut  with  a  knife  and 
fuses  at  the  remarkably  low  temperature  of  about  30°C. 
It  is  not  easily  soluble  in  nitric  acid  but  dissolves  readily 
in  dilute  hydrochloric  acid  or  an  alkaline  hydrate  solution 
with  the  evolution  of  hydrogen. 

353.  The  Aluminum  Group.  —  The  metals  of 
this  group  form  feebly  basic  sesquioxides.  Their  sulphates 
form  double  salts  with  the  sulphates  of  the  alkali  metals. 
Common  alum  is  a  familiar  example  of  these  double  salts. 
They  crystallize  in  regular  octohedrons. 

(a.)  The  apparent  quantivalence  of  these  elements  may  be  seen  in 
the  symbols  of  their  compounds,  in  which  the  double  atom  of  each 
metal  acts  as  a  hexacl.  Some  of  these  known  compounds  are  sym- 
bolized thus : 

A!203         AI3S3  AI3CI6  AI2(S04)3  AI2(N03)6 

In203  In2S3  In2CI6  In2(SO4)3  In3(N03)6 

Ga203         Ga2S3  Ga2Cla  Ga2(S04)3  Ga2(N03)6 

V  353.  The  Cerium  Group.— This  group  consists 
of  six  rare  metals,  the  separation  of  which,  one  from  the 
other,  is  very  difficult.  Two  of  them,  erbium  and  terbium, 
have  not  yet  been  isolated.  The  metals  of  this  group  are 
contained,  chiefly  as  silicates,  in  several  rare  minerals 
found  in  Scandinavia,  Siberia  and  Greenland.  Cerium  is 
the  best  known.  It  is  malleable  and  ductile  and,  when  it 
is  scraped  with  a  knife  or  struck  with  a  piece  of  flint,  the 
metallic  particles  struck  off  burn  with  great  brilliancy. 
Cerium  burns  in  a  flame  with  a  light  more  brilliant  than 
that  of  magnesium.  It  forms  both  cerous  and  eerie  com- 


278 


THE    CERIUM    GROUP. 


§353 


pounds.    When  these  metals  are  present,  they  are  easily 
distinguished  by  means  of  the  spectroscope. 

(a.)  The  following  table  exhibits  the  leading  known  properties 
and  compounds  of  these  metals  : 


If 

! 

Elements. 

•g 

*i 

<K 

Compounds. 

|  ;   -S    8 

I 

Cerium  

Cel41.8 

6.7 

(  Ce.O,  CeaS3 
1  Ce  O 

CeCI3 

Ce2(SOj 

Ce(N03):, 

Ce.XC03)s 

Didymium  .... 

Di 

147 

6.5 

Di.O, 

DiaS3 

DiCI3 

D..CSOJ: 

Di(NOs)5 

Di2(COs)s 

Erbium 

Fr 

1  69(  ?) 

EraO, 

Terbium 

Tr 

98 

Tr,O, 

Tr./SO  ). 

Lanthanum  .  .  . 

La 

139 

6.1 

La.,O, 

La.jS;, 

LaCI, 

La..(S04), 

La(NO,)3 

La2(CO:))3 

Yttrium  

Y 

93.5 

.... 

Y2O3 

Y2S3 

YCI3 

Y3(SOJ3 

Y(NO3), 

Y2(C03)3 

'  -    '    /tf-Alf'^1'                               -.(^Vfr 
EXERCISES.                                '. 

1.  (a )  Assuming  AP",  write  the  graphic  symbol  for  Ala03.    (b.)  As- 
suming Al'"'.     (c.)  Assuming  AP'. 

2.  (a.)  How  many  cu.  cm.  of  0  may  be  obtained  by  the  electrolysis 
of  10  g.  of  H20  ?    (&.)  How  many  of  H  ? 

..   3.  Calculate  the  weight  of  air  required  to  burn  a  ton  of  coal,  hav- 
ing the  percentage  composition  :  C,  88.42  ;  H,  5.61  ;  0,  etc.,  5.97. 

4.  Write  equations  for  the  following  reactions  :  (a.)  Copper  and 
nitric  acid  yield  copper  nitrate,  nitric  oxide  and  water,     (b.)  Mercury 
and  sulphuric  acid  yield  mercuric  sulphate,  sulphurous  anhydride 
and  water. 

5.  The  symbol  for  water  was  formerly  written  HO  and  (for  some 
years  subsequently)  H302.     What  inconsistency  do  you  see  in  these 
symbols  other  than  any  based  on  atomic  weights  ? 

6.  (a.)  What  would  be  a  systematic  chemical  name  for  microcosm ic 
salt  (NaNHAH£04  +  4HaO)?    (&.).  What  wei 

iphic ^symbol  for  AI3F6,  assudfirig^  the  metal 


this  salt  ?.> 

7.  Write  the  'g 
a  tetrad. 


f'H   in   10  #.  of 


be 


• 


t: 


METALS    OF    THE     IRON     GROUP. 


r. 


IRON. 


Symbol,  Fe  ;  specific  gravity,  7.8  ;  atomic  weight,  56  m.  c.;  quan- 
ticalen.ce,  2,  4  and  6. 

354.  Occurrence. — Iron,  the  most  important  of  all 
the  metals,  is  seldom  found  native.     Metallic  iron  of  me- 
teoric origin  has  been  found.     This  element  is  widely  dis- 
tributed, traces  of  it  being  found  in  the  blood  of  animals, 
in  the  ashes  of  most  plants,  in  spring,  river  and  ocean 
waters,  and,  in  fact,  in  nearly  all  natural  substances.    Its 
ores  are  numerous,  abundant  and  comparatively  pure. 

(a.)  The  most  important  iron  ores  are  specular  iron  or  hematite 
(Fe303);  limonite  or  brown  hematite  [Fe403(HO)G]  :  magnetite  or 
magnetic  iron  (Fe304)  ;  spathic  iron  (FeC03)  and  clay  iron-stone  or 
black-band  iron-stone,  which  is  a  spathic  iron  containing  clay  or  sand 
with  other  substances  and  generally  found  as  nodules  or  bands  in 
the  coal  measures. 

(&.)  The  value  of  an  iron  ore  often  depends  more  upon  the  nature 
of  its  impurities  than  upon  its  percentage  of  Fe. 

355.  Calcination. — The  hydrate,  the  carbonate  and 
the   "  black-band "  iron  ores  are  generally  prepared  for 
smelting  by  roasting  them.    In  this  way  the  water  and 
carbon  dioxide  are   expelled,  the  ores  are  oxidized  and 
rendered  more  porous,  while  any  sulphides  that  may  be 
present  are  oxidized  and  the  sulphur  driven  off. 


280  IB  ON.  §  356 

356.  Preparation ;   Direct  Process,— The  na- 
tive or  artificial  oxides,  are  sometimes  reduced  in  "  bloomery 
forges  "  of  simple  construction.     The  broken  ore  is  heated 
with  charcoal,  the  fire  being  supplied  with  a  hot-air  blast. 
The  charcoal  deoxidizes  the  ore,  the  reduced  iron  collects 
as  a  pasty  mass  called  "  the  bloom"  which  separates  from 
the  fusible  mass  called  "  slag."    The  "bloom  "  needs  only 
to  be  hammered  to  yield  a  good  quality  of  wrought  iron. 
The  process  is  simple  and  time-honored  but  expensive  on 
account  of  the  quantity  of  fuel  consumed  and  of  iron  lost 
in  the  slag. 

357.  Preparation;    Indirect   Process.  —  The 
indirect  process  of  forming  wrought  or  malleable  iron  con- 
sists of  two  distinct  stages :  1st,  the  production  of  cast 
iron  from  the  ore ;  2d,  the  production  of  wrought  iron 
from  the  cast  iron. 

358.  Cast  Iron. — This  is  a  carbonized,  fusible  pro- 
duct of  the  blast  furnace,  which  will  soon  be   described. 
The  preparation  of  cast  iron  involves  four  steps.     The 
first  is  the  preliminary  calcination  of  the  ore  for  the  pur- 
poses mentioned  in  §  355.     With  some  ores,  this  step  is  not 
necessary ;  in  other  cases,  it  is  effected  in  the  upper  part 
of  the  blast  furnace.     The  second  step  is  the  reduction  of 
the  oxide  to  the  metallic  state  by  heating  it  with  carbon. 
The  third  step  is  the  separation  of  the  silicious  or  calcare- 
ous impurities  of  the  ore  by  fusion  with  some  other  sub- 
stance, called  a  flux,  to  form  a  fusible  slag.     The  fourth 
step  is  the  carbonizing  and  melting  of  the  iron.     This  ad- 
dition of  the  carbon  renders  the  product  more  easily  fusi- 
ble.    The  melted  iron  is  finally  run  into  rough  moulds  and 
forms  semi-cylindrical  masses,  known  as  pig-iron. 

359.  The   Blast  Furnace.  —  The  blast  furnace 


§359 


IRON. 


281 


(Fig.  113)  is  a  shaft  of  fire-brick  and  masonry,  often  cased 
in  iron  plate.  It  is  from  50  to  90  feet  in  height  and  from 
14  to  18  feet  in  diameter  at  the  "belly"  or  widest  part. 
Alternate  layers  of  coal,  coke,  flux  and  ore  are  introduced 
from  above  as  the  heated  mass  settles  in  the  furnace  and 


FIG.  113. 

the  molten  iron  and  slag  are  drawn  off  below.  With  ores 
that  contain  siliceous  impurities,  the  flux  is  limestone; 
with  ores  that  contain  calcareous  impurities,  the  flux  is 
clay  or  of  a  siliceous  character.  The  fusible  silicate  formed 
by  the  union  of  the  flux  and  the  impurities  of  the  ore  con- 


2S2  IRON.  §  359 

stitnte  the  slag.  A  blast  of  hot  air  is  forced  in  at  the 
hearth,  through  pipes,  tt  called  tuyeres  (pronounced  tiveers) 
and  the  combustion  thus  sustained  and  invigorated.  The 
melted  iron  settles  to  the  crucible  or  lowest  part  of  the 
hearth  while  the  melted  slag  floats  upon  its  surface  and 
overflows  a  dam  in  an  almost  continuous  stream.  When 
the  crucible  is  full  of  molten  metal,  the  latter  is  drawn  off 
through  a  tapping  hole  which  is,  at  other  times,  stopped 
with  sand. 

(a.)  The  throat  of  tlie  blast  furnace  is  closed  with  a  cup  and  cone 
arrangement,  as  shown  in  Fig.  113.  The  cone,  b,  is  lowered  by  a 
chain  when  a  charge  is  to  be  introduced.  When  &  is  raised  against 
the  cup,  a,  the  throat  of  the  furnace  is  closed  and  the  escape  of  the 
blast  furnace  gases  into  the  air  is  prevented.  These  gases  consist  of 
very  hot  hydrocarbons  with  H,  CO,  C02,  \\,etc.  These  heated  gases, 
some  of  which  are  combustible,  are  conveyed  by  pipes  from  the 
throat  of  the  furnace  and  utilized  for  heating  the  tuyeres  and  the 
boilers  for  steam  power  purposes. 

(&.)  The  chemical  changes  that  take  place  in  the  blast  furnace  are 
of  great  interest  and  have  been  carefully  studied,  but  our  knowledge 
of  them  is  still  far  from  complete.  At  the  lower  part,  where  the 
temperature  is  highest,  the  fuel  burns  to  C02 ;  in  the  widest  part  of 
the  furnace,  the  C03  is  reduced  by  the  glowing  C  to  CO  ;  at  a  point 
still  further  up,  where  the  temperature  is  from  GOO'C.  to  900°C.  the 
CO  reduces  the  ore  to  a  spongy  mass  of  metallic  iron.  As  the  spongy 
metal  descends  to  the  bottom  part  of  the  furnace,  near  the  bolly 
where  the  temperature  is  from  1000°C.  to  1400°C.,  it  takes  up  C, 
becoming  thus  more  fusible,  melts  completely  and  runs  down  into 
the  crucible  below  the  level  of  the  mouth  of  the  tuyeres.  In  the 
meantime,  the  fusible  slag  has  been  formed  and  melted.  It  then 
floats  on  the  surface  of  the  heavier  iron  in  the  crucible  and  thus  pro- 
tects the  metal  from  the  oxidizing  action  of  the  blast. 

(c.)  Cast  iron  is  generally  contaminated  with  S,  Si,  P,  and  fre- 
quently with  Mn,  and  contains  from  two  to  six  per  cent,  of  C. 

(d.)  Pig  iron  includes  while  cast  iron,  gray  cast  iron  and  several  in- 
termediate varieties  called  mottled  cast  iron.  White  cast  iron  con- 
tains all  of  its  C  in  chemical  union.  When  it  is  dissolved  in  HCI  or 
H2S04,  various  hydrocarbons  are  formed  that  give  a  disagreeable 
odor  to  the  H  evolved.  In  gray  cast  iron,  part  of  the  C  crystallizes 


IRON. 


283 


out  in  cooling,  forming  graphite,  which  is  left  in  the  form  of  black 
scales  when  the  iron  is  dissolved  in  an  acid.  White  cast  iron  con- 
tracts on  solidifying  ;  gray  ca&t  iron  expands  on  solidifying  and  is, 
therefore,  the  better  adapted  for  foundry  use  although  it  is  less 
easily  melted.  Spiegeleisen  is  a  variety  of  white  cast  iron  very  rich 
in  C,  and  containing  Mn.  It  is  very  hard  and  crystalline  and  is  used 
in  the  Bessemer  process  of  steel  manufacture.  When  it  contains 
25  per  cent .  or  more  of  Mn  it  becomes  granular  and  is  called  ferro- 
manganetz. 

36O.  Wrought  Iron.  —  Cast  iron  is  changed  to 
wrought  iron  by  a  process  called  puddling,  in  which  most 
of  the  carbon,  silicon,  sulphur  and  phosphorus  of  the  cast 
iron  is  burned  out.  Wrought  iron  contains  less  than 
half  of  one  per  cent,  of  carbon,  its  malleability  increasing 
and  its  fusibility  decreasing  as  the  quantity  of  carbon  di- 
minishes. It  may  be  welded  at  a  red  heat. 

(a.)  A  puddling  furnace  is  shown  in  elevation  in  Fig.  114  and  in 


FIG.  114. 
section  in  Fig.  115.     The  charge  of  pig  iron  and,  generally,  a  quan- 


284 


IRON. 


§360 


tity  of  iron  scale  or  other  iron  oxide,  are  placed  in  the  bed,  h,  sepa- 
rated from  the  fire  grate  by  the  fire  bridge,  &,  and  from  the  chimney 
by  the  flue  bridge,  d.  A  strong  draft  is  furnished  by  the  chimney 
and  controlled  by  a  damper  at  the  top  of  the  chimney,  which  dam]  er 
may  be  opened  or  closed  by  the  workman.  After  the  charge  has 


FIG.  115. 

been  melted,  it  is  vigorously  stirred  or  puddled,  and  the  C,  S,  Si 
and  P  thus  removed  The  iron  becomes  less  easily  fusible  by  the 
'  decarbonizing.  The  pasty  mass  is  then  carried  from  the  furnace,  the 
fusible  slag  removed  and  the  porous  Fe  welded  into  a  solid  mass  by 
hammering  or  squeezing. 

Experiment  283.— Place  about  15  g.  of  pulverized  Fe203  in  the  bulb 
of  the  tube,  c,  Fig.  116.    Pass  a  current  of  dry  H  through  the  bul  b  tube. 


FIG.  116. 

When  all  of  the  air  has  been  driven  from  the  apparatus,  heat  the 
oxide  to  redness.     When  it  has  been  reduced  to  a  black  powder  of 


§  362  IRON.  285 

metallic  Fe,  remove  the  lamp  and  allow  the  contents  of  the  bulb  to 
cool  in  a  current  of  H. 

Fe303  +  3H2  =  Fe2  +  3H20. 

This  black  powder  may  be  set  on  fire  by  a  lighted  splinter.  It 
oxidizes  so  easily,  that  it  will  take  fire  if  emptied  from  the  bulb 
tube  into  the  air  while  it  is  still  hot. 

361.  Properties  of  Iron. — Iron  may  be  prepared 
in  a  pure  state  by  reducing  the  oxide  with  hydrogen  or  car- 
bon monoxide.     In  the  compact  state,  it  is  ductile,  malle- 
able, tenacious  and  highly  magnetic.     It  does  not  oxidize 
in  dry  air  at  ordinary  temperatures.     When  heated  in  air, 
an  oxide  forms.     This  "  scale  oxide"  is  beaten  off  by  ham- 
mering and  may  be  found  in  considerable  quantities  about 
a  blacksmith's  anvil.      Iron  oxidizes  or  rusts  rapidly  in 
moist  air.     It  is  readily  acted  upon  by  dilute  hydrochloric, 
nitric  or  sulphuric  acid.    It  fuses  at  a  white  heat  but  soft- 
ens before  it  melts.     In   this  softened  state  it  may  be 
welded.     Sand  or  borax  is  sprinkled  upon  the  heated  sur- 
faces that  are  to  be  united  and  a  fusible  slag  is  thus  formed 
with  the  coating  film  of  oxide.     When  the  two  pieces  of 
iron  are  then  hammered  together,  the  slag  is  driven  out 
leaving  clean  surfaces  of  iron  in  contact.     The  blows  of 
the  hammer  bring  the  metallic  particles  within  the  range  of 
molecular  attraction  (Ph.,  §  46,  a),  cohesion  binds  them 
fast  and  the  iron  is  welded. 

(a.)  Commercial  iron  is  never  pure.  If  P  is  present  as  an  impurity, 
the  iron  is  brittle  when  cold  and  is  said  to  be  "  cold-short."  The 
presence  of  S  renders  the  iron  brittle  when  hot ;  the  iron  is  then  said 
to  be  "  red  short." 

362.  Oxides    of  Iron.  —  Iron  forms  three  well- 
known  oxides;  ferrous  oxide  (iron  monoxide,  FeO),  ferric 
oxide  (iron  sesquioxide,  Fe203)  and  ferroso-ferric  oxide 


286  IRON.  §  362 

(magnetic  oxide  of  iron,  Fe304).     The   ferric  and  mag- 
netic oxides  are  found  native  as  iron  ores. 

(a.)  FeO  may  be  prepared  by  heating  ferrous  oxalate  in  a  close  ves- 
seXor  by  passing  H  over  Fe803  heated  to  300°C.  If  exposed  to  the 
air  within  a  few  hours  after  its  preparation,  it  oxidizes  so  rapidly  as 
to  take  fire. 

(&.)  Fe20:}  is  one  of  the  most  important  iron  ores.  This  oxide  is 
prepared  artificially  for  use  as  a  paint.  A  fine  variety  is  known  as 
jeweller's  rouge,  and  is  used  for  polishing  glass  and  metals.  Another 
artificial  variety  is  called  crocus,  and  is  also  used  for  polishing  metals. 

(c.)  Fe304  is  found  in  large  quantities  as  the  richest  of  iron  ores. 
Many  specimens  attract  iron  and  are  called  loadstones  (Ph.,  §  302). 
Scale  oxide  is  chiefly  Fe304.  We  may  consider  Fe304  as  a  mixture 
or  compound  of  FeO  and  Fe30s. 

Experiment  284.  —  Cover  a  teaspoonful  of  fine  iron  filings  with  three 
or  four  times  its  volume  of  dilute  H2S04.  When  the  evolution  of 
H  ceases,  pour  off  the  clear  liquor,  add  a  few  drops  of  strong  HN03 
and  boil  the  liquid.  The  yellowish-red  color  is  due  to  the  presence 
of  ferric  sulphate.  Add  N  H  4  H  0  to  the  solution  and  shake  the  liquids 
together.  A  red  precipitate  of  ferric  hydrate  will  be  formed  ;  it  may 
be  collected  upon  a  filter. 


363.  Iron  Hydrates.—  -Fm-o^s  hydrate  (FeH202) 
is  obtained  by  treating  a  solution  of  a  pure  ferrous  salt 
with  potassium  or  sodium  hydrate  in  absence  of  air.    The 
precipitate  thus  formed  is  an   unstable,   white  powder, 
which  rapidly  oxidizes  with  change  of  color,  evolution  of 
heat  and,  sometimes,  incandescence  when  exposed  to  the 
air.     Ferric  hydrate  (Fe2H606)  is  prepared  by  precipi- 
tating a  moderately  dilute  solution  of  a  ferric  salt(e.#., 
Fe2CI6)  with  an  excess  of  ammonia  water.    When  freshly 

jprepared,  it  is  one  of  the  best  antidotes  for  arsenic  (§  247). 

f\ 

364.  Iron  Sulphides.  —  Iron  and  sulphur  form  two 

well-known  compounds,  iron  monosulphide  (FeS)  and  iron 
disulphide  (FeS2).     Iron  monosulphide  is  formed  by  di- 


§  366  IRON.  287 

rect  union  of  its  constituents.  A  roll  of  brimstone  may 
be  made  to  penetrate  a  red  hot  plate  of  steel  or  wrought 
iron  with  formation  of  melted  sulphide.  It  is  generally 
prepared  by  gradually  throwing  a  mixture  of  three  parts 
of  iron  filings  and  two  parts  of  sulphur  into  a  red  hot  cru- 
cible. It  is  the  cheapest  source  of  hydrogen  sulphide  and, 
hence,  very  important.  Iron  disulphide  occurs  widely  dis- 
tributed in  nature  as  pyrite  (or  iron  pyrites).  It  is  largely 
used  in  the  manufacture  of  sulphuric  acid  and  ferrous 
sulphate. 

365.  Iron  Salts. — Iron  forms  two  well  defined  series 
of  salts.    In  the  ferrous  series,  the  iron  atom  acts  as  a  dyad 
as  it  does  in  ferrous  oxide.    In  the  ferric  series,  the  iron 
double  atom  (Fe2)VI  acts  as  a  hexad  as  it  does  in  ferric 
oxide.    (See  also  Ex.  2,  page  289.) 

(a.)  Solutions  of  ferrous  salts  readily  absorb  0  and  precipitate  ferric 
salts  unless  an  excess  of  acid  is  present.  They,  therefore,  act  as 
powerful  reducing  agents  and  are  largely  used  as  such  in  the  labora- 
tory and  the  arts. 

(6.)  The  ferric  salts  are  readily  reduced  to  the  corresponding  ferrous 
compounds. 

366.  Iron    Chlorides. — The  halogen  elements  form,   with 
iron,  both  ferrous  and  ferric  compounds.     These  series  are  well  typi- 
fied by  ferrous  and  ferric  chlorides.     Ferrous  chloride  (FeCI2)  is  best 
prepared  by  passing  a  current  of  hydrochloric  acid  gas  over  an  ex- 
cess of  red  hot  iron  filings  or  wire.    Ferric  chloride  (Fe2CI6)  may  be 
prepared  by  passing  a  current  of  chlorine  through  a  solution  of  fer- 
rous chloride  until  the  solution  smells  strongly  of  the  gas  and  then 
displacing  the  excess  of  chlorine  by  passing  a  current  of  carbon  di- 
oxide through  the  warm  liquid.     This  solution,  when  concentrated, 
has  a  dark  brown  color  and  an  oily  consistency. 

Experiment  %85. — Dip  a  piece  of  cotton  cloth  into  a  solution  of 
nut  galls  and  allow  it  to  dry;  dip  it  into  a  solution  of  green  vitriol 
and  hang  it  up  in  a  moist  atmosphere.  It  will  be  permanently 
colored  by  the  precipitation  of  an  insoluble  iron  tannate. 


288  IRON.  §  367 

367.  Iron  Sulphates,  etc.  —  Ferrous  sulphate 
(green  -vitriol,  FeS04,  7H20)  is  made  in  immense  quan- 
tities by  exposing  pyrite  (FeS2)  to  the  action  of  the  at- 
mosphere, as  an  incidental  product  in  the  manufacture 
of  copper  sulphate  or  by  dissolving  iron  in  dilute  sul- 
phuric acid.  It  is  largely  used  in  the  arts.  Ferric  sulphate 
[Fe2(S04)3]  is  prepared  by  the  action  of  nitric  acid 
upon  an  acidulated  solution  of  ferrous  sulphate: 

6FeS04  +  3H2S04  +  2HN03  =  3Feo(S04)3  +  2NO  +  4H30. 

(a.)  Ferrous  nitrate  [Fe(N03)2]  is  a  very  soluble,  unstable  com- 
pound.  Ferric  nitrate  [Fe3(N03)6]  is  prepared  by  dissolving  Fein 
H  N  03.  It  is  largely  used  as  a  mordant  in  dyeing  and  calico  printing. 
Ferrous  carbonate  (FeC03)  is  found  as  an  iron  ore. 

36 §.  Iron  Cyanides. — Iron  unites  with  cyanogen  to  form 
ferrous  and  ferric  cyanides.  The  most  important  iron  cyanides,  how- 
ever, are  double  compounds.  When  crude  potash  (K2C03)  is  fused 
with  nitrogenous  organic  matter,  such  as  horn,  feathers,  dried  blood, 
leather  clippings,  etc.,  in  the  presence  of  iron  filings,  the  fused  mass 
leached  with  water  and  the  liquid  evaporated,  large  yellow  crystals 
are  formed.  These  crystals  are  potassium  ferrocyanide  [K8(CN)12Fe2, 
3H20],  better  known  as  yellow  prussiate  of  potash.  This  compound 
is  important  as  it  serves  as  the  point  of  departure  for  the  preparation 
of  nearly  all  the  cyanogen  compounds.  It  may  also  be  formed  by  the 
additiou  of  a  ferrous  salt  to  an  aqueous  solution  of  potassium  cyanide. 
12KCN  +  2FeS04  =  K8(CN)18Fe3  +  2K2S04.  The  tendency  to  form 
this  salt  is  so  great  that  metallic  iron  is  rapidly  dissolved  when 
heated  in  such  a  solution  of  potassium  cyanide.  When  a  current  of 
chlorine  is  passed  into  a  solution  of  potassium  ferrocyanide,  the  reac- 
tion \\Q\fapotassmmferricyanide  [K6(CN)13Fe2]  or  red  prussiate  of 
potash.  The  class  of  compounds  known  as  Prussian-blues  are  chiefly 
compounds  of  ferrous  and  ferric  cyanides,  generally  united  with 
potassium. 

Experiment  S86. — Half  fill  each  of  two  test  glasses  with  a  very  di- 
lute solution  of  FeS04  and  each  of  two  other  glasses  with  a  similar 
solution  of  Fe2(SO4)3.  Prepare  a  dilute  solution  of  K8Cy12Fe.,  and 
one  of  K6Cy12Fe,.  Add  a  drop  of  K8Cy12Fe2  to  one  of  the  glasses 
of  Fe2(S04)3 ;  a  blue  precipitate  will  be  formed  and  color  the 
liquid.  In  similar  manner,  add  K8Cy18Fe2  to  FeS04  ;  no  color  will 


368 


IRON. 


289 


appear.  In  similar  manner,  add  K6Cy12Fe2  to  FeS04  ;  the  blue  color 
will  appear.  In  similar  manner,  add  KGCy12Fe2  to  Fe2(S04)3  ;  no 
color  will  appear.  In  the  name  of  K8Cy12Fe2,  the  pupil  will  notice 
a  contraction  for  ferrous  ;  a  similar  contraction  for  ferric  appears  in 
the  name  of  KGCy]2Fe2.  When,  in  this  experiment,  we  brought 
two  -OILS  or  two  -ic  compounds  together,  no  color  was  produced. 
When  an  -ous  compound  and  an  -ic  compound  were  brought  together, 
a  blue  color  was  formed.  Potassium  ferro-  and  ferricyanides  act 
thus  with  all  ferrous  and  ferric  salts  and  may,  consequently,  be  used 
as  tests  to  detect  the  presence  of  these  salts  in  any  solution  or  to  dis- 
tinguish between  them. 

Experiment  387.  —  Soak  a  piece  of  cotton  cloth  in  a  solution  of 
Fe2(S04)3  and  then  dip  it  into  an  acidulated  solution  of  K8Cy12Fe2. 
Prussian  blue  is  precipitated  upon  the  cloth  which  is  thus  colored. 


K 


EXERCISES. 

• 

1.  Name  the  compounds  symbolized  as  follows:  FeBr2  ;  Fe2Br 


C12N]2Fe2 


Fe2(S04) 


ft 


2.  State  two  things  indicated  by  the  following  graphic  symbol : 
Cl     Cl 

CI— Fe-Fe-CI. 

<!.  <;. 

8.  A  certain  iron  oxide  has  a  molecular  weight  of  232  m.  c.  and  «  ^ 
contains  27.6  per  cent,  of  0.     What  is  the  symbol  ? 

4.  (a.)  What  weight  of  FeS  will  be  needed  to  yield,  II.  of  H2S? 
(I).}  How  much  air  will  be  required  to  burn  the  H2S?  f yv 

5.  What  weight  of  marble  is  needed  to  convert  a  ton  of  soda  crys- 
tals into  bicarbonate  of  soda?     ••7  /ru 

6.  How  many  liters  of  air  will  be  necessary  to  burn  a  liter  each  of 
(a.)  marsh  gas,  (6.)  olefiant  gas  and  (c.)  acetylene  v  ' 

7.  The  vapor  density  of  NH4CI  is  one  fourth  of  the  number  of 
microcriths  in  its  molecular  weight,    (a.)  Why  is  it  said  to  be  ab- 
normal?   (&.)  Can  you  suggest  an  explanation  o£JJje  variation  ? 


290 


STEEL. 


§369 


STEEL, 

369.  Steel.— Steel  is  intermediate  between  cast  iron 
and  wrought  iron  in  respect  to  properties  and  chemical 
composition.  It  contains  from  0. 7  to  2  per  cent,  of  carbon, 
Its  most  characteristic  property  is  that  of  acquiring  re- 
markable hardness  by  beating  and  quickly  cooling  as  by 
plunging  into  water.  Steel  thus  hardened  cannot  be 
worked  wiiji  a  file  and  is  very  brittle  and  elastic.  .  The 
hardness  and  brittleness  are  lessened  by  tempering,  which 
process  consists  in  heating  the  steel  to  220°C.  —  331°C.  and 
then  cooling  it  quickly.  The  hardest  temper  is  obtained 
at  the  lowest  temperature.  The  workman  judges  the  tem- 
perature by  observing  the 
tints  on  the  surface  of  the 
metal.  These  colors  are 
caused  by  different  thick- 
nesses of  the  oxide  formed. 

37O.  The  Cemen- 
tation Process.  —  A 

few  years  ago,  the  only 
method  of  making  steel 
was  to  decarbonize  cast 
iron  in  the  puddling  fur- 
nace and  then  to  recarbon- 
FIG.  117.  ize  the  wrought  iron  in  the 

cementation  furnace  (Fig.  117.)    The  furnace  contains  two 


§  371  STEEL.  291 

square  boxes,  c,  made  of  infusible  fire  clay,  into  which  are 
put  bars  of  wrought  iron  packed  in  soot  or  powdered 
charcoal.  Six  or  seven  tons  of  iron  are  put  into  each  box. 
A  fire  is  built  on  the  hearth,  y,  and  the  boxes  kept  at  a 
temperature  of  1000°C.  or  1200°C.  for  from  seven  to  ten 
days.  At  the  end  of  the  process,  it  is  found  that  the  metal 
has  become  finer  grained,  more  brittle,  more  fusible,  that 
its  surface  has  a  blistered  appearance,  whence  the  name, 
"  blister  steel,"  and  that  carbon  has  penetrated  the  metal, 
although  the  iron  has  not  been  melted  or  the  carbon  vapor- 
ized. Several  hypotheses  have  been  advanced  to  account 
for  the  phenomena  involved,  but  none  of  them  is  satis- 
factory. 

371.  The  Bessemer  Process.— In  this  process, 
steel  is  made  by  decarboniz-  e.. 

ing  cast  iron  by  a  current  of 
air  forced  through  the  melted 
metal  in  an  egg-shaped  vessel 
called  the  converter  (Fig.  1 18.) 
The  converter  is  made  of  iron 
plates  lined  with  infusible  ma- 
terial. The  bottom  is  a  shal- 
low wind  box,  <?,  from  which 
numerous  small  openings  lead 
into  the  converter.  The  ves- 
sel is  supported  upon  trun-  FIG.  118. 
nions,  one  of  which,  i,  is  hollow  and  connected  with  the 
wind  or  tuyere-box.  When  the  interior  of  the  converter 
has  been  heated  to  whiteness,  it  is  turned  upon  its  trun- 
nions until  the  line,  ac,  is  horizontal.  Melted  cast  iron  is 
then  run  through  the  mouth  into  the  belly,  abc.  The  air 
blast  is  then  turned  on  through  i,  the  converter  raised  into 


292  STEEL.  §  371 

an  upright  position,  the  compressed  air  bubbling  through 
the  molten  metal,  burning  out  the  carbon  and  silicon  and 
combining  with  part  of  the  iron.  This  combustion  in  the 
converter  causes  intense  heat  which  keeps  the  iron  melted 
despite  its  approach  to  the  less  easily  fusible  condition  of 
wrought  iron.  During  this  time,  the  flame  that  rushes 
from  the  mouth  of  the  converter  is  accompanied  by  a  mag- 
nificent display  of  sparks  due  to  the  combustion  of  iron 
particles  (Exps.  38-40).  When  this  pyrotechnic  exhibi- 
tion has  continued  for  six  or  eight  minutes,  the  exact 
moment  being  indicated  to  the  trained  eye  of  the  overseer 
by  the  appearance  of  the  flame,  the  converter  is  turned 
until  the  melted  iron  leaves  the  tuyere  openings  uncovered 
and  the  air  blast  is  stopped.  The  decarbonized  iron  is  now 
recarbonized  by  the  addition  of  a  carefully  determined 
quantity  of  spiegeleisen.  The  molten  mass  is  poured  into 
a  ladle  and  thence  into  moulds,  and  the  cast  steel  worked 
up  under  the  hammer  or  in  the  rolling  mill.  In  less  than 
half  an  hour,  from  five  to  twelve  tons  of  cast  iron  has 
been  converted  into  steel. 

(a.)  All  of  the  movements  of  the  converter,  ladle,  cranes,  etc.,  are 
produced  by  hydraulic  power  and  controlled  by  a  workman  at  "  the 
piano,"  as  the  assemblage  of  wheels  and  levers  is  called. 

(&.)  Steel  might  be  produced  by  stopping  the  oxidation  before  all 
of  the  C  of  the  cast  iron  had  been  burned  out.  But  the  difficulties 
arising  from  too  nearly  complete  oxidation  and  the  practical  impossi- 
bility of  making  successive  "  blows  "  yield  the  same  quality  of  steel 
led  to  the  adoption  of  the  present  plan.  Bessemer  steel  is  largely 
used  in  the  construction  of  railway  tracks,  bridges,  etc. 

312.  The  Siemens-Martin  Process.  — In  this 
process,  hydrocarbon  gases  and  air  are  heated,  mixed  and 
burned,  the  flame  passing  over  a  hearth  containing  a  charge 
of  cast  iron  and  wrought  iron  scrap  mixed  in  definite  pro- 


§  374  STEEL.  293 

portions.  The  melted  metal  is  run  from  the  hearth  into 
a  ladle  containing  the  proper  amount  of  spiegel  or  ferro- 
manganese,  after  which  the  steel  is  ready  for  casting.  The 
sides  and  top  of  the  furnace,  the  exposed  parts  of  the  flues, 
and  the  hearth  are  made  of  such  highly  infusible  material 
as  silica  brick. 

373.  Crucible  Steel.— A  very  fine  quality  of  steel 
is  made  for  edge  tools  by  fusing,  in  graphite  crucibles,  a 
fine  quality  of  wrought  iron  with  powdered  charcoal.     The 
crucibles  are  closely  covered  and  heated  in  a  coke  fire. 
The  steel  is  cast  into  ingots  and  worked  into  bars  under 
the  hammer. 

374.  Malleable  Iron.  —  Intermediate  between  cast 
iron  and  wrought  iron  is  an  article,  known  in  commerce 
as  "malleable  iron."  Small  castings  are  made  of  white  cast 
iron  for  a  great  variety  of  purposes,  such  as  for  harness, 
wagons,  agricultural  implements,  etc.     These  castings  are 
packed  with  iron  scale  or  oxide  in  "annealing  boxes  "  and 
then  heated  to  a  high  temperature.     The  carbon  of  the 
cast  iron  is  thus  removed  in  great  part  and  the  material 
changed  from  white,  hard  and  brittle  cast  iron  to  black, 
soft  and  tough  "malleable  iron."    Articles  thus  made  are 
nearly  as  tough  as  they  would  be  if  made  of  wrought  iron 
and  much  less  expensive.    Compare  the  process  with  the 
cementation  process  for  making  steel, 


.  7/£    ^ 

294  ,      STEEL. 

C^.    -  £3.' 
'     f  & 

EXERCISES. 

•      "r,  « 

1.  Give  the  names  and  atomic  weights  of  the  elements  represented 
by  the  following  symbols  :  Fe,  Mg,  Hg,  Zn,  Ca,  C,  Cl,  I,  P,  K,  N,  Na, 
S',  Ag,  Br.  Cu,  Fl,  H,  Pb,  0,  Al,  Sb,  Si. 

:  •.    .       .,•'''•     '' 


§374 

tyW'ti 


Equation 

H2             H 

h          Cl, 

= 

2HCI 

Names  of  molecules. 
Nos. 
Weight  u  molecule. 
Total  weights 

Hydrogen 

2m.  <?. 

2  m  c.  used. 

Chlorine 
1 
71  m.  c. 
71  m  c  used 

Yield 

Hydrochloric  acid. 
.  2 
36.5  m.  c. 
73  m  c   obtained 

Gaseous  volumes  
Laboratory  Exp  

2  unit  volumes  " 
500  cw.  cm. 

2  unit  volumes  " 
500  cu.  cm. 

4  unit  volumes  " 
1  liter. 

2.  According  to  the  above  or  a  similar  schedule,  write  out  the  fol- 
lowing equations  : 

(a.}  2H20  +  2CI2  =  4HCI  +  02. 

(6.)  2CO  +  02  =  2C02. 
~te.)  C03  +  C(solid)  =  2CO. 

(d.)  2NH3  =  N3  +3H2. 

(e.)  2NH3  +  3CI2  =  N2  +  6HCI. 
-(/.)  NH4N03(solid)  =  N2O  +  2H20. 

(g.)  MnO,  +  4HCI  =  MnCI2  +  CI3  +  2H20. 

(h.)  S02  +  2H20  +  CI2  =  H2S04  +  2HCI. 


2Mn03  +  2H2S04  =  2MnS04 


02. 


3.  Why  is  it  not  practicable  to  obtain  more  than  a  small  quantity 
of  mixed  H  and  0  by  electric  sparks  in  an  atmosphere  of  steam  ? 


&VU4 


UA( 


§  376  MANGANESE.  295 


MANGANESE,    COBALT    AND    NICKEL. 


MANGANESE:  symbol,  Mn  ;  specific  gravity,  8 ;  atomic  weight, 
54.8  m.  c.  ;  quantivaknce,  2  (4  and  6). 

375.  Manganese. — The  principal  source  of  manga- 
nese is  the  dioxide  (Mn02)  which  is  found  in  nature  as  the 
mineral  pyrolusite.     Among  the  other  manganese  ores  are 
braunite  (Mn203)  and*  hausmanite  (Mn304).    The  metal 
is  seldom  prepared  but  may  be  obtained  by  heating  one  of 
the  oxides  with  carbon  at  an  intense  white  heat  for  several 
hours.    It  is  very  hard  and  brittle,  easily  soluble  in  dilate 
acids,  and  decomposes  warm  water  with  the  evolution  of 
hydrogen.     When  pure,  it  is  almost  as  infusible  as  plati- 
num and  oxidizes  easily  in  the  air.      It  is  best  kept  in 
petroleum.    It  is  feebly  magnetic  (Ph.,  §  310)  and  forms  a 
beautiful  alloy  with  copper. 

376.  Oxides. — At  least  five  distinct  manganese  oxides 
are  known: 

(a.)  Manganese  monoxide  (manganous  oxide,  MnO)  is  powerfully 
basic. 

(&.)  Red  oxide  of  manganese  (mangano-manganic  oxide,  Mn304) 
may  be  considered  a  compound  of  MnO  and  Mn203.  It  is  analogous 
to  magnetic  iron  ore. 

(c.)  Manganese  sesquioxide  (manganic  oxide,  Mn303)  is  isomor- 
plious  with  AI203  andFe303.  The  corresponding  hydrate  [Mn202 
(H0)a]  is  found  in  nature  as  manganite. 

(d.)  Manganese  dioxide  (manganese  peroxide,  black  oxide  of  man- 
ganese, Mn02)  is  the  most  important  manganese  ore.  It  is  used  in 
preparing  0  and  Cl,  and  in  coloring  glass.  At  a  bright  red  heat,  it 
yields  up  0  and  is  reduced  to  Mn304. 


296  COBALT.  §  376 

(e.)  Manganic  anhydride  (Mn03)  and  manganic  acid  (H2Mn04)  have 
not  yet  been  isolated  but  several  mangauates  (e.  y.,  K,Mn04)  are  well 
known.  K2Mn04  is  isotnorphous  with  K2S04. 

(/.)  Manganese  heptoxide  (Mn  .,  07)'  is  an  anhydride,  yielding  per 
manganic  acid  (H2Mn2O8)  when  brought  into  contact  with  H2O. 

Experiment  288.  —  Pat  a  small  quantity  of  Mn02  into  an  ignition 
tube  and  add  enough  H2S04  to  wet  it  thoroughly.  Arrange  the 
tube  as  shown  in  Exp.  56.  Heat  gently,  collect  the  gas  and  find  out 
what  it  is.  Q* 

Experiment  289.—  Dissolve  0.5  g.  of  oxalic  acid  (C2H204)  crystals 
in  50  en.  cm.  of  H20  ;  add  5  cu.  cm.  df  H2S04  ;  warm  to  about  GO°C. 
To  this  colorless  solution,  add,  drop  by  drop,  a  solution  of  K2Mn208. 
The  K2Mn208  gives  up  0  and  converts  the  C«H204  to  H30  and  C02 
and  is  reduced  to  MnS04  and  K2S04,  -in  which  process,  its  rich 
color  is  destroyed.  If  an  excess  of  the  potassium  permanganate  be 
added,  it  will  not  be  decolorized. 

Experiment  290.  —  Repeat  the  last  experiment,  using  FeSO  ,  instead 
of  C2H204.  The  K2Mn208  oxidizes  the  ferrous  to  ferric  sulphate. 

Note.  —  Knowing:  the  reactions  for  these  experiments  and  the  quan- 
tity of  K-jMrioOg  used,  before  the  decoloration  ceases,  the  quantity 
of  oxidizable  matter  (C2H204  or  FeS04)  present  is  easily  calculated 
(quantitative  analysis). 

Experiment  291.  —  Mix  some  K2Mn208  and  Ba02  in  a  mortar. 
Transfer  the  mixture  toaflask  and  moistenit  with  H2S04.  Astarch 
and  potassium  iodide  test  paper  held  at  the  mouth  of  the  flask  will 
be  colored  blue.  Explain  the  discoloration. 

377.  Manganese  Salts.  —  A  few  years  ago,  the 
manganates  and  permanganates  were  found  only  in  the 
laboratory  where  they  were  used  as  oxidizing  agents. 
They  are  now  manufactured  on  the  large  scale  for  use  as 
disinfectants. 


COBALT  :  symbol,  Co  ;  specific  gravity,  8.G  ;    atomic  weight, 
58.6  m.  c. 

378,  Cobalt.—  Cobalt  is  not  found  free,  except  in 
meteoric  matter.  Its  ores  are  not  widely  distributed. 
The  metal  may  be  obtained  from  an  artificially  prepared 


§  379  NICKEL.  297 

oxide  by  reduction  with  hydrogen  or  from  a  chloride  by 
ignition.  It  is  harder  than  iron  and  melts  more  easily.  It- 
is  magnetic,  malleable  and  very  tough.  When  pure,  it  is 
silvery  white. 

(a.)  Cobalt  has  three  oxides,  tlie  monoxide  (cobaltous  oxide,  CoO), 
tlie  sesquioxide  (cobaltic  oxide,  Coa03)  and  an  intermediate  com- 
pound, cobaltous-cobaltic  oxide  (Co304)  which  corresponds  to  the 
magnetic  oxide  of  iron.  There  are  also  two  series  of  salts,  the  co- 
baltous and  the  cobaltic. 

Experiment  292. — Partly  fill  a  test  tube  with  a' concentrated  solu- 
tion of  chloride  of  lime.  Add  a  small  quantity  of  Co->03  and  heat 
gently.  A  brisk  effervescence  takes  place.  Test  the  gas  evolved 
with  a  glowing  splinter.  The  calcium  hypochlorite  contained  in  the 
bleaching  powder  is,  under  the  catalytic  influence  of  the  sesquioxide, 
decomposed.  Write  the  reaction. 

Experiment  293. — Prepare  an  aqueous  solution  of  CoC 1 3  by  dis- 
solving CoO  or  Co303  in  HCI.  Make  a  drawing  with  this  nearly 
colorless  solution.  Heat  the  sketch  to  about  150°C.  ;  it  will  appear 
blue.  Breathe  upon  it  ;  the  blue  color  will  disappear. 

•  Experiment  294. — To  2  cit.  cm.  of  the  pink  solution  of  CoCI3  in  a 
test  glass,  add  an  equal  quantity  of  sodium  silicate  or  "  water  glass," 
well  diluted  so  as  to  be  thin.  A  blue  precipitate  appears. 

CoCI2  +  Na3Si03  =2NaCI  +  CoSi03, 
or    2CoCI3  +  Na4Si5012  =  4NaCI  +  Co2Si5012. 


NICKEL;   symbol,   Ni ;  specific  gravity,  8.9;  atomic  weight, 
58.6  m.  c. 

379.  Nickel.— Mckel  is  almost  always  associated  with 
cobalt  in  either  terrestrial  or  extra-terrestrial  matter.  It 
is  a  lustrous,  white  metal,  ductile,  malleable,  magnetic, 
very  hard  and  susceptible  of  a  high  polish.  It  can  be 
welded.  It  is  largely  used  for  plating  articles  of  iron  and 
steel  to  protect  them  from  rusting.  It  is  also  used  in 
coinage  and  for  making  alloys.  German  silver  is  an  alloy 
of  nickel,  copper  and  zinc. 


298  NICKEL.  §  379 

(a.)  The  oxides  of  Ni  are  the  monoxide  (nickel  oxide,  NiO)  and  the 
sesquioxide  (nickel  peroxide,  NiaOs).  Nickel  salts  are  derived  from 
the  monoxide.  The  inoit  important  salt  is  the  nitrate. 

38O.  The  Iron  Group.—  The  metals  of  this  group 
form  basic  monoxides;  they  also  form  sesquioxides  and 
corresponding  series  of  salts.  Cobalt  and  nickel  have  the 
same  atomic  weight  and  are  seldom  separated  in  nature. 

•    EXEECISES. 

1.  Pyrolusite  may  be  reduced  to  Mn304  by  intense,  li  eat.  Write 
the  reaction.  , 


2.  Write  a  graphic  symbol  for  KsMn04.  A 

3.  Write  two  graphic  symbols  for  K8Mrio08. 

4.  Write  a  graphic  symbol  for  manganese  sesquioxide,  represent- 
ing the  metal  as  a  dyad.     ^     ~       . 

5.  Write  a  graphic  symbol  for  nickel  sesquioxide,  representing  the 
metal  as  a  tetrad.  /    •*•    A   •  **  ^ 

6.  Write  a  graphic  symbol  for  Mn"03.   *  ."..  ;/  '  ' 

7.  Which  is  the  correct  symbol  for  nickel  hydrate,    NiHO    or 
NiH203  V    Give  a  reason  for  your  answer. 

.    8.  (a.)  Write  the  symbol  for  jpobaltous  hydrate.    (&.)  For  cobaltic. 
hydrate.  *  '  &>M>K 

9.  (a.)  Write  the  equation  representing  the  reaction  for  Exp.  289. 
(b.)  For  Exp.  290. 

10.  Write  the  symbol  for  the  potassium  salt  of  the,  hydrate  of 
manganese  heptoxi^e.    What  is  the  name  of  the  salt  ?  f\iA\#\ 

•!  ^ 

O+H^iM^^i^W^t 


W    ^^        «">* 


METALS    OF    THE    CHROMIUM    GROUP. 

CHROMIUM:  symbol,  Cr;  specific  gravity,  4.78 ;  atomic  weight, 
52,4  m.  c. 

381.  Chromium. — Chromium  is  a  rather  rare,  almost 
sil  ver  white  metal  and  is  not  found  free  in  nature.  Its  chief 
ore  is  chromite  or  chrome  iron  ore  (FeCr204).  It  forms  the 
green  coloring  matter  of  emerald,  serpentine  and  other 
minerals.  The  fused  metal  is  almost  as  hard  as  the  diamond 
and  melts  less  easily  than  platinum.  At  a  white  heat,  it 
combines  directly  with  oxygen  or  nitrogen,  forming,  with 
the  latter,  a  brown  chromium  nitride.  It  is  a  good  con- 
ductor of  electricity  and  is  magnetic.  The  presence  of  0.5 
to  0.75  per  cent,  of  this  metal  renders  steel  ("  chromium 
steel ")  harder  than  carbon  alone  can  do.  Several  chro- 
mium compounds  are  somewhat  extensively  used  in  the 
arts. 

(a.)  Chromium  forms  three  oxides  ;  the  monoxide  (chromous  oxide, 
CrO) ;  the  sesquioxide  (chromic  oxide,  green  oxide  of  chromium, 
Cr203)  and  the  trioxide  (chromic  anhydride,  Cr03). 

(&.)  Chromic  trioxide  may  be  obtained  by  treating  potassium  di- 
chromate  with  H2S04.  The  red  crystals  thus  formed  may  be  dis. 
solved  in  H20  forming  chromic  acid  (H2Cr04). 

(c.)  Potassium  chromate  (yellow  chromate  of  potash,  K2Cr04)  is 
used  in  the  arts,  but  the  potassium  dichromate  (bichromate  of  potash, 
K2Cr207)  is,  by  far,  the  most  important  of  the  Cr  compounds,  as  it 
serves  as  the  starting  point  in  the  preparation  of  nearly  all  of  the 
others.  It  crystallizes  in  beautiful  garnet  red  prisms  and  is  prepared 
in  large  quantities  from  FeCr304.  Chrome  yellow  is  a  lead  chromate 
(PbCr04).  It  is  largely  used  as  a  pigment. 

(d.)  Chrome  alum  [K2S04,  Cr2(S04)s,  24H20]  is  used  in  dyeing, 
calico  printing  and  tanning. 


300  MOLYBDENUM.  §  382 

Experiment  295. — Dissolve  15  g.  of  pulverized  K2Cr207  in  100  cu.cm. 
of  warm  H30.  When  the  solution  has  cooled,  add  15  cu.  cm.  of 
strong  H2S04,  and  pour  it  into  a  porcelaiu  dish  placed  in  cold  t-LO. 
When  the  liquid  is  cool,  slowly  stir  in  8  cu.  cm.  of  C2H60  and  set 
the  whole  aside  for  a  day.  At  the  end  of  that  time,  crystals  of 
K2S04,  Cr2(S04)3,  24H20  will  cover  the  bottom  of  the  dish. 


MOLYBDENUM  ;   symbol,    Mo  ;   specific  gravity,  8.6 ;  atomic 
weight,  95.8  m.  c. 

382.  Molybdenum. — This  metal  is  rare  and  has  been  but 
imperfectly  studied.  It  is  prepared  by  heating  its  trioxide  or  one  of 
its  chlorides  to  redness  in  a  current  of  hydrogen.  It  has  a  silver 
white  color,  and  is  highly  infusible.  Molybdenum  has  four  known 
oxides  :  MoO  ;  *Mo.,03 ;  Mo02 ;  Mo03,  Molybdic  acid  has  the  com- 
position, H2Mo04. 


TUNGSTEN  :   symbol,  W ;  specific  gravity,  19.1   (?) ;  atomic 
weight,  183.5  m.  c. 

3§3.  Tungsten. — Tungsten  is  a  rare  metal,  being  found  in  only 
a  few  minerals,  the  most  important  of  which  is  wolfram,  a  tungstate 
of  iron  and  manganese.  It  is  said  that  the  addition  of  tungsten  to 
steel  improves  the  hardness  and  tenacity  of  the  latter.  Tungsten 
forms  two  oxides,  W02  and  W03.  Tungstic.acid  has  the  composi- 
tion, H8W04. 


URANIUM  :    symbol,  U  ;   specific  gravity,  18.33;  atomic 
weight,  240  m.  c. 

3§  I.  I  r;« ni II in. — This  is  a  rare  metal,  the  chief  ore  of  which 
is  pitch  blende,  an  impure  uranium  oxide  (U308).  The  metal  is  mal- 
leable and  hard  and  has  a  color  resembling  that  of  nickel.  It 
has  two  well  known  oxides,  the  dioxide  (uranyl,  uranous  oxide, 
U03)  and  the  trioxide  (uranyl  oxide,  uranic  oxide,  U03).  These 
oxides  mix  to  form  the  intermediate  oxides,  U205  (black  oxide  of 
uranium  =  U03  +  U03)  and  U308  (<?reen  oxide  of  uranium 
—  U02  +  2U03).  Uranium  dioxide  is  a  basic  oxide  ;  by  dissolving 
it  in  strong  acids,  green  uranous  salts  are  formed.  Uranium  trioxide 
is  an  acid  forming  oxide.  The  uranic  salts  are  yellow  and  most  of 
them  have  a  remarkable  power  of  fluorescence,  which  they  impart 
to  glass  (Ph.,  §  371,  31).  Uranium  yellow  (Na2U207)  is  largely  used 


§  384  URANIUM.  301 

for  giving  the  beautiful  yellowish  green  color  to  glass  known  as 
"  uranium  glass." 

Note.  —  Uranium  was  formerly  classed  in  the  iron  group,  its  atomic 
weight  given  as  120  m.  c.  and  its  oxides  symbolized  by  UO  and 
Uo03.  The  metals  of  this  group  form  acid-forming  trioxides  and 
yield  very  characteristic  salts. 

4£r6) 

EXEKCISES. 

v  y 

1.  Assuming  Crtobe  a  tetrad,  write  the  graphic  symbol  for  CrsC!6. 


2.  Write  the  graphic  symbol  for  K2Cr04.        ^ 


3.  Read  the  following,  naming  each  symbolized  sifostance  by  its 
full  systematic  name:  FeS04,  7H30  is  pale  green;   MnS04,  ?H2O 
is  pale  pink;   CoS04,  7H2O  is  bright  red;   NiS04,  7H20  is  bright 
green  ;  and  CrS04,  7H20  is  palo  blue. 

4.  Can  you  detect  any  difference  in  the  apparent  quantivalence  of 
any  two  metals,  the  compounds  of  which  are  symbolized  in  the  third 
Exercise  ? 

5.  Write  the  empirical  symbol  for  hydrated  sulphuryl  oxide.    ' 


*/V\/v 

r 


V, 

METALS    OF    THE    TIN     GROUP. 

TIN  :  symbol,  Sn  ;  specific  gravity,  7.29 ;  atomic  weiglit,  118 
m.  c. ;  quantitalence,  2  and  4. 

385.  Source. — The  principal  tin  ore  is  a  dioxide 
called  casserifce  or  tin-stone.    It  is  found  in  but  few  locali- 
ties, the  principal  ones  being  Cornwall  in  England,  Banca 
and  Malacca  in  India.     It  has  also  been  found  in  Austra- 
lia, New  Hampshire  and  California.     Native  tin  has  been 
found  in  small  quantities. 

386.  Preparation. — Tin  is  prepared  by  pulverizing, 
washing  and  roasting  the  ore  and  then  smelting  it  with 
charcoal  or  anthracite. 

Experiment  296.  —  The  familiar,  so-called  "  tin-ware  "  is  only 
tinned  ware,  iron  coated  with  tin.  Heat  a  piece  of  tinned  iron  over 
the  lamp  until  the  Sn  has  melted ;  thrust  the  plate  into  cold  H20  to 
harden  the  Sn  quickly  ;  remove  the  smooth  surface  of  the  metal  by 
rubbing  it  first  with  a  bit  of  paper  moistened  with  dilute  aqua  regia, 
and  then  with  paper,  wet  with  soda-lye.  Notice  the  crystalline 
figures  thus  produced,  resembling  frost  upon  a  window  pane. 

Experiment  297. — If  you  have  a  cake  of  Sn,  wash  one  surface  of  it 
with  dilute  aqua  regia  until  the  crystalline  forms,  above  mentioned, 
appear. 

Experiment  298. — Hold  a  bar  of  Sn  near  the  ear  and  bend  the  bar. 
Notice  the  peculiar  crackling  sound.  Continue  the  bending  and 
notice  that  the  bar  becomes  heated.  The  phenomena  noticed  seem 
to  be  caused  by  the  friction  of  the  crystalline  particles. 

387.  Properties. — Tin  is  a  lustrous,  soft,   white 
metal,  that  melts  at  about  230°C.     It  is  highly  malleable, 


§  389  TIN.  303 

slightly  tenacious,  ductile  at  100°C.  and  brittle  at  200°C. 
It  has  a  marked  tendency  to  crystallize  on  cooling  from  a 
melted  condition.  It  unites  readily  with  oxygen,  chlorine, 
sulphur  and  phosphorus  when  heated  with  them.  It  is 
not  easily  tarnished  by  even  moist  air  but  is  easily  acted 
upon  by  acids.  Heated  in  the  air,  it  burns  to  the  dioxide 
(stannic  oxide,  Sn02).  It  forms  two  series  of  compounds, 
the  stannous  and  the  stannic. 

388.  Uses. — Tin  is  largely  employed  in  the  form  of 
foil  (Ph.,  §  353)  and  as  a  coating  for  other  metals;  e.  g,., 
copper  used  for  bath  tubs  or  cooking  utensils,  sheet  iron 
for  "  tin-plate  "  and  iron  tacks  and  as  a  lining  for  lead 
water  pipes.    It  is  largely  used  in  making  numerous  alloys. 

(a.)  Bronze  and  bell  metal  are  alloys  of  Cu  and  Sn.  Plumber's 
solder  and  pewter  are  alloys  of  Pb  and  Sn.  Britannia  metal  is  an 
alloy  of  Cu,  Sb  and  Sn.  The  "  silvering  "  of  mirrors  is  an  amalgam 
of  Hg  and  Sn. 

(b.)  The  Sn  of  tinned  ware  is  sometimes  adulterated  with  Pb  which 
is  less  costly.  This  alloy  of  Pb  and  Sn  will  oxidize  much  more 
readily  than  Sn  will.  This  lead  oxide  is  easily  dissolved  by  the 
C2H4Oa  of  vinegar  forming  the  dangerous  poison,  lead  acetate,  or 
"  sugar  of  lead."  The  various  acids  of  our  common  fruits  unite  with 
the  lead  oxide  to  form  salts  and  all  of  the  soluble  lead  salts  are  poison- 
ous. Dr.  Kedzie,  President  of  the  Michigan  State  Board  of  Health, 
says  :  "  It  is  an  astonishing  fact  that  a  large  proportion  of  the  tinned 
wares  in  the  market  is  unfit  to  use  because  of  the  large  quantity  of 
lead  with  which  the  tin  is  alloyed."  As  these  compounds  are  cumu- 
lative poisons,  he  adds  :  "  A  person  may  not  be  poisoned  by  one  or 
two  small  doses  but  even  if  a  very  minute  dose  is  taken  for  a  long 
time,  the  person  may  be  broken  in  health  or  even  lose  his  life."  As 
a  test  for  this  Pb  adulteration,  he  recommends  that  a  drop  of  HNOS 
be  placed  on  the  tinned  surface  and  rubbed  over  a  space  as  large  as 
a  dime,  that  the  metal  be  warmed  until  dry  and  that  two  drops  of  a 
solution  of  KI  be  placed  on  the  spot.  "  If  the  tin  contains  lead,  a 
bright  yellow  iodide  of  lead  will  be  formed  on  the  spot." 

389.  Tin  Compounds. — Tin  forms  two  oxides,  the  monox- 
ide (staimous  oxide,  SnO)  and  the  dioxide  (stannic  oxide,  Sn02).    The 


304  r/y    GROUP.  §  389 

former  is  basic  ;  the  latter  is  both  a  basic  and  an  acid  forming  oxide. 
Their  compounds  are  designated  as  stannous  and  stannic  salts.  Stan- 
nic acid  (H,Sn03)  is  a  white  solid.  Stannous  chloride  (Sn2CI4) 
is  prepared  by  dissolving  tin  in  warm  hydrochloric  acid.  Tin  tetra- 
chloride  (stannic  chloride,  SnCI4)maybe  prepared  by  passing  cljlo- 
rine  over  tin-foil  or  f  used  tin  in  a  retort.  If  a  quick  stream  of 
chlorine  be  forced  through  melted  tin,  heat  and  light  are  evolved. 
Stannic  chloride  is  a  colorless  liquid,  which,  when  treated  with 
one-third  its  weight  of  water,  forms  a  crystalline  mass  called  "  butter 
of  tin." 


TITANIUM  :  symbol,  Ti  ;  atomic  weight,  48  m.  c. 

390.  Titanium.  —  This  is  a  rare  metal,  not  found  in  the  me- 
tallic state.  It  has  the  remarkable  power  of  combining  directly  with 
free  nitrogen  at  bigh  temperatures,  forming  three  distinct  nitrides, 
Ti3N2,  Ti3N4,  Ti2N2.  Titanium  dioxide  (Ti02)  is  trimorphous. 


ZIRCONIUM  :'  symbol,  Zr ;  specific  gravity,  4-15  ;  atomic  weight, 
90  m.  c. 

391.  Zirconium.— Tbis  rare  metal  has  been  obtained  in  the 
form  of  an  iron  gray  powder  and  in  a  crystallized  state.  The  crys- 
talline variety  can  be  ignited  only  at  the  temperature  of  the  oxy- 
hydrogen  flame  or  in  chlorine  at  a  red  heat.  It  has  only  one  known 
oxide  (zirconia,  Zr02),  which  is  white  and  infusible. 


THORIUM:  symbol,  Th ;  specific  gravity,  7.7;  atomic  weight, 
231.5  m.  c. 

392.  Thorium  .—This  rare  metal  is  a  constituent  of  thorite 
and  a  few  other  rare  minerals.  It  has  been  prepared  as  a  gray 
powder  that  takes  an  iron  gray  lustre  when  burnished.  It  takes  fire 
when  heated  in  the  air.  Its  oxide  (Th02)  is  sometimes  called  thoria. 

Note. — The  metals  of  this  group  are  closely  connected  with  the 
non-metal,  silicon,  in  that  they  form  dioxides  corresponding  to  Si08 
and  present  other  chemical  analogies.  Ti  and  Zr  occupy  a  position 
intermediate,  in  many  respects,  between  carbon  and  silicon  on  one 
hand  and  the  metals  on  the  other. 


, 
§  392  WI\TIN.  305 


1.  Define  normal)  acid./basic  and  double  salts.    Illustrate 

2.  A  molecule  of  a  certain  oxide  contains  one  atom  of  Sn  and  has 
a  weight  of  150 -m.  c.     What  is  its  symbol  ?    ^J/vO^ 

3.  Write  the  symbol  for  triferric  tetroxide.  F~£A  $14 

4.  A  number  of  salts  having  the  general  symbol  M'HS08  were 
called  by  their  discoverer,  "hydrqsulphites."    What  is  their  proper 
systematic  name?  fac~*'i(^^ 

5.  Show  how  far  each  of  the  following  compounds  agrees  with  the  ' 
definitions  of  acid,  base  and  salt : 

(a.}  Chlorides  of  H,  K,  Al,  P  and  S. 

(6.)  Oxides  of  H,  K  and  C. 

(c.)  Hydrates  of  K,  Na,  S08  and  Ca. 

6.  How  many  liters  of  marsh  gas  will  weigh  as  much  as  25  I.  of 
ethene  ?  I>f6  $L 

7.  A  certain  Compound  has  a  molecular  weight  of  CO  m.  c.    Its 
centesimal  composition  is  as  follows :  40  o£  C  ;  53.4  of  0  and  6.6  of 
H.     What  is  the  com  pound  &  <}  f^^  $  .    C£ 

S.  Indicate  the  quantivalence  of  each  of  the  following  radicals : 
S,  0,  Cl,  HO,  NH4,  PO,  S02. 
9.  Write  the  graphic  symbol  for  phosphoryl  trichloride.  ' 

V—     ^/    /; 
**K:'.         * 

TTT^.  /.  /  ItjM'MU  \'  M;fo(f*h  ,      (J 


wM^w 
%ffa 

i 


"vi 

METALS  OF  THE  GOLD  GROUP. 

|3f°GoLD:  symbol,  Au  ;  specific  gravity,  19.265;  atomic  weight, 
106.2  m.  c. ;  quantivalence,  1  and  3. 

393.  Occurrence. — Gold  is  widely  distributed  in 
nature  but  in  only  a  few  places  is  it  found  in  quantities 
sufficient  to  repay  the  cost  of  obtaining  it.     It  is  generally 
found  in  the  native  state  alloyed  with  silver.     Native  gold 
is  found  in  the  quartz  veins  that  intersect  metamorphic 
rocks  and  in  the  alluvial  deposits,  called  placers,  formed  by 
the  disintegration  of  gold  bearing  rocks. 

(a.)  The  richest  deposits  of  Au  are  in  California,  Colorado,  Nevada 
and  Australia.  Native  Au  is  found  in  crystals,  nuggets,  grains  and 
scales.  While  the  particles  are  sometimes  so  small  as  to  be  invisible 
in  even  "  paving  "  quartz,  a  single  nugget,  weighing  184  pounds  and 
valued  at  £8376,  10s.  6d.,  was  found  in  Australia.  Gold  compounds 
are  also  found  in  nature.  Two  mines  in  Nevada  produced  in  1877, 
$15,597,263  in  Au  and  $17,061,587  in  Ag. 

394.  Preparation. — In  quartz  mining,  the  ore  is 
first  pulverized.      The  gold  is  then  extracted  from  the 
powdered  mineral  by  means  of  mercury.     The  gold  amal- 
gam thus  formed  is  subjected  to  distillation.     In  "  placer 
digging,"  the  lighter  constituents  of  the  alluvial  deposit 
are  washed  away,  the  heavier  gold  remaining  in  the  "  wash- 
pan"  or  "cradle."      In  "hydraulic    mining,"    immense 
streams  of  water  are  directed,  under  great  pressure,  against 
the  surface  of  the  auriferous  deposit.     In  this  way,  great 


§  396  GOLD.  307 

quantities  of  sand,  clay  and  gravel  are  disintegrated  and 
hurried  forward  in  a  turbid  torrent,  from  which  the  heavy 
gold  particles  settle  into  interstices  previously  prepared  in 
the  tunnel,  through  which  the  muddy  mass  is  caused  to 
flow.  The  amount  of  labor  and  capital  expended  in  Cali- 
fornia upon  canals,  aqueducts,  shafts  and  tunnels  for 
hydraulic  mining  is  very  great. 

Experiment  299. — Add  a  few  drops  of  a  strong  solution  of  AuCI3  to 
a  liter  of  H20.  Into  this  dilute  solution,  drop  one  or  two  pieces  of 
P,  the  size  of  a  mustard-seed,  and  place  the  whole  in  the  sunlight. 
In  the  course  of  a  few  hours,  the  water  will  have  a  distinct  purplish 
tint,  This  will  deepen  in  color  until  finally,  if  the  solution  has  the 
proper  strength,  a  beautiful  ruby-red  liquid  will  be  obtained.  The 
color  of  this  liquid  is  due  to  finely  divided  metallic  gold. 

395.  Properties. — Gold  is  a  brilliant,   beautiful, 
orange-yellow  metal.     It  is  the  most  malleable  and  ductile 
of  the  metals.     It  may  be  beaten  into  leaves  not  more 
than  0.0001  mm.   thick ;    1  g.  of  it  may  be  drawn  into 
3240  m.  of  wire.     It  is  softer  than  silver,  nearly  as  soft  as 
lead.   It  fuses  at  about  1100°C.,  and  volatilizes  at  very  high 
temperatures.     It  is  not  attacked  by  oxygen  or  water  at 
any  temperature.     It  does  not  dissolve  in  any  simple  acid 
except  selenic  but  dissolves  readily  in  aqua  regia  or  in  any 
other  acid  liquid  that  evolves  chlorine. 

(d.}  One  ounce  of  Au  leaf  may  be  made  to  cover  189  sq.  ft. ,  while 
280,000  leaves  placed  one  upon  another  measure  only  one  inch  in 
thickness.  One  grain  of  Au  will  gild  two  miles  of  fine  Ag  wire,  the 
deposit  of  Au  being  about  0.000002  mm.  thick.  Ordinary  gold  leaf 
transmits  green  light.  Au  may  be  precipitated  in  so  fine  a  state  that 
it  remains  suspended  in  the  liquid,  causing  it  to  appear  ruby -red 
by  reflected  light  or  blue  by  transmitted  light.  The  red  color  of  ruby 
glass  is  due  to  the  presence  of  Au  in  a  finely  divided  state.  Au  is 
sometimes  called  the  "king  of  metals." 

396.  Uses.  — Gold  is  used  for  coinage,  jewels,  gilding 


308  PLATINUM.  §  396 

and  other  purposes,  for  which,  it  is  well  adapted  by  its 
beautiful  color  and  lustre,  its  unalterability  and  compara- 
tive rarity.  Pure  gold  is  so  soft  that  coins  and  jewels  made 
of  it  would  soon  wear  out.  It  is,  therefore,  hardened  by 
alloying  with  copper.  American  and  French  gold  coins 
contain  one-tenth  copper  ;  British  gold  coins,  one-twelfth. 

(a.)  The  purity  of  Au  in  jewels  is  estimated  in  carats,  pure  Au  being 
"  24  carats  fine."  An  alloy  containing  f  gold  is  "  16  carats  fine." 

(&.)  The  compounds  of  Au  are  of  little  chemical  interest.  There 
are  two  oxides,  the  monoxide  (aurous  oxide,  Au80)  and  the  trioxide 
(auric  oxide,  gold  sesquioxide  (Au203).  There  are  two  chlorides,  AuCI 
and  AuCI3.  Aurous  cyanide  (AuCN)  dissolved  in  a  solution  of  KCN 
is  used  in  electro  gilding  (Ph.,  §  399,  a). 


PLATINUM  :  symbol,  Pt ;  specific  gravity,  21.5  ;  atomic,  iceiyht, 
196.7  m.  c. 

397.  Occurrence,  etc. — Platinum  is  found  only  in 
the  native  state,  but  very  seldom  pure.  The  so  called 
"  platinum  ore  "  is  an  alloy  of  the  metals  of  this  group, 
with  iron,  copper,  etc.  It  is  found  in  the  Ural  mountains, 
in  Brazil,  Borneo,  California  and  other 
places.  The  preparation  of  pure  pla- 
tinum is  a  matter  of  great  difficulty. 
For  fusing  the  metal  on  the  large  scale, 
a  crucible  made  of  two  pieces  of  lime 
is  used  with  a  compound  blowpipe 
(Fig.  119).  The  upper  part  of  the 
blowpipe  is  made  of  copper ;  the  lower 
part,  of  platinum.  Coal  gas  is  gener- 
ally used  instead  of  hydrogen.  The 
lime  of  the  crucible  successfully  resists  FIG. 
the  high  temperature  produced  and  absorbs  the  slags 
formed  during  the  operation. 


§397 


PLATINUM. 


309 


Experiment  300. — Boil  0.5  g.  of  Pt  in  small  fragments  in  a  tea- 
spoonful  of  aqua  regia  as  long  as  the  metal  seems  to  be  acted  upon. 
Pour  the  liquid  into  an  evaporating  dish,  add  aqua  regia  to  the  re- 
maining Pt  and  proceed  as  before,  continuing  thus  until  all  of  the  Pt 
has  been  dissolved.  Evaporate  the  solution  to  dryness  upon  the 
water  bath.  Dissolve  this  residue  (PtC  I4)  in  H20. 

Experiment  301. — Heat  a  few  drops  of  the  solution  of  PtCI4  in  a 
test-tube.    Notice  the  odor  of  the  gas  evolved.     Hold  a  strip  of  mois- 
tened litmus  at  the  mouth  of  the  test  tube.    It  will  be  bleached. 
2PtCI4  =  Pt2  +  4CI2. 

'  Experiment  302. — Pour  a  teaspoonful  of  a  solution  of  NH4CI  into  a 
test  tube,  acidulate  it  with  HCI,  and  to  it  add  a  drop  of  the  solution  of 
the  PtCI4  just  prepared.  A  yellow,  insoluble  powder  (2NH4CI,PtCI4) 
will  soon  be  precipitated.  Repeat  the  experiment,  taking  enough  of 
the  solutions  to  make  half  a  teaspoonful  of  the  yellow  precipitate, 
being  careful  that  at  last  there  shall  be  a  slight  excess  of  free  NH4CI 
rather  than  of  PtCI4  in  the  overlying  liquid.  Allow  the  precipitate 
to  settle,  separate  it  from  the  clear  liquor  by  decantation  and  partly 
dry  it  at  a  gentle  heat.  When  the  precipitate  has  acquired  the  con- 
sistence of  slightly  moistened  earth,  transfer  it  to  a  cup-shaped  piece  of 
Pt  foil,  and  heat  it  to  redness  in  the  gas  flame,  until  fumes  of  NH4CI 
are  no  longer  driven  off.  A  gray,  loosely-coherent,  sponge-like  mass 
of  metallic  platinum  will  remain  in  the  cup  ;  it  is  platinum  sponge. 

Experiment  303. — Repeat  Exp.  30,  using  either  illuminating  gas 
or  H*. 

Experiment  304- — Fill  a  spirit  lamp  with  a  mixture  of  C2H60  and 
(C2H5).jO.  Suspend  a  spiral  of  Pt  wire  over  the  wick  (Fig.  120)  and 
light  the  lamp.  When  the  wire  is  red  hot,  blow  out  the  flame.  The 
mixed  vapors  rising  from  the  wick  are  oxidized  by  the  heated 
Pt;  the  spiral  is  thus 
kept  brightly  incandes- 
cent. This  is  Davy's  glow 
lamp.  The  experiment 
may  be  varied  by  suspend- 
ing the  spiral  in  a  loosely 
covered  test  glass  contain- 
ing (C2H5)20,  as  shown 
in  Fig.  121,  or  by  heating 
a  bit  of  Pt  foil  in  a  Bunsen 
flame  and  blowing  out  the 
flame.  The  foil  will  glow 
and  may  reignite  the  gas  if 
held  near  enough  to  the  burner. 


FIG  120. 


FIG.  121. 


310  PLATINUM.  §  398 

398.  Properties.— Platinum  is  a  heavy,  soft  metal 
of  tin-white  color.  It  is  infusible  at  the  highest  tempera- 
ture of  the  blast  furnace  but  yields  before  the  oxyhydrogen 
flame.  Its  melting  point  has  heen  estimated  at  2000°C. 
It  is  very  malleable  and  so  ductile  that  it  may  be  drawn 
into  a  wire  less  than  0.001  mm.  in  diameter.  Like  gold,  it 
has  little  affinity  for  the  other  elements.  It  is  not  oxi- 
dized by  oxygen,  water,  nitric  or  sulphuric  acid  at  any 
temperature.  It  dissolves  in  aqua  regia  more  slowly  than 
gold  does.  It  also  dissolves  in  chlorine  water.  Like  iron, 
it  may  be  welded  at  a  white  heat. 

(a.)  Red  hot  Pt  absorbs  3.8  volumes  of  H,  which  it  gives  off  when 
heated  in  a  vacuum,  the  surface  of  the  Pt  becoming  then  covered  with 
hubbies.  Similarly,  H  is  absorbed  by  Pt,  at  the  negative  electrode  in 
the  electrolysis  of  H20  (Exp.  12),  the  occluded  H  being  given  off 
when  the  current  is  reversed  so  as  to  make  the  Pt  the  positive 
electrode. 

(&.)  0  is  not  absorbed  by  Pt  but  it  is  condensed  on  a  clean  surface 
of  the  metal.  Thus,  mixtures  of  0  or  air  with  H,  CO,  C2H4,  C2H60 
or  (C2H5)20  vapor,  and  other  easily  inflammable  gases  or  vapors  may 
be  made  to  combine,  sometimes  slowly,  sometimes  quickly,  some- 
times with  explosion  (Exps..  30  and  52). 

(0.)  The  preparation  of  platinum  sponge  has  been  illustrated  in 
Exps.  300  and  302.  Owing  to  its  large  surface,  compared  with  its 
volume,  it  is  able  to  condense  large  quantities  of  0. 

(d.)  Platinum-black  is  a  form  of  metallic  Pt,  even  more  finely  di- 
vided than  platinum-sponge.  It  is  a  soft,  dull,  black  powder.  It  can 
absorb  more  than  800  times  its  volume  of  0.  When  boiled  in  H20 
and  dried  in  a  vacuum  over  H3S04,  it  absorbs  0  from  the  air  so 
rapidly  that  the  mass  becomes  red  hot.  If  upon  the  powder,  when 
cooled  after  such  absorption  of  0,  some  C2H60  or*  (C2H5)20  be 
dropped,  the  oxidation  of  the  liquids  will  heat  the  metal  red  hot. 

(e.)  Pt  unites  readily  with  other  metals  forming  alloys  which  are 
generally  more  easily  fusible  than  the  element. 


§  400  PALLADIUM.  311 

399.  Uses.  —  On  account  of  its  infusibility  and  its 
chemical  inertness,  platinum  is  invaluable  to  the  chemist. 
In  the  laboratory,  it  is  used  for  crucibles,  evaporating 
dishes,  stills,  tubes,  spatulas,  forceps,  wire,  blowpipe  tips, 
etc.  In  sulphuric  acid  manufacture,  large  platinum  stills 
and  siphons  (§  152,  c)  are  used  for  concentrating  the  acid. 
As  its  rate  of  expansion  is  nearly  equal  to  that  of  glass 
(Ph.,  §  485,  a),  it  is  used  in  the  manufacture  of  eudiom- 
eters, Geissler  tubes,  incandescent  electric  lamps,  etc. 

(a.)  On  account  of  Pt  forming  easily  fusible  alloys,  care  should  be 
had  not  to  heat  Pt  utensils  with  an  easily  fusible  metal,  e.g.,  Pb,  Bl, 
Sn  or  Sb,  or  any  easily  reducible  compound  of  a  metal.  They  should 
not  be  used  for  fusion  with  nitre,  the  alkalies,  or  alkaline  cyanides. 
They  should  not  be  heated  in  contact  with  P  or  As  nor  brought  into 
direct  contact  with  burning  charcoal. 

(&.)  "  Without  Pt,  it  would  be  impossible,  in  many  cases,  to  make 
the  analysis  of  a  mineral.  The  mineral  must  be  dissolved.  Vessels 
of  glass  and  all  non-metallic  substances  are  destroyed  by  the  means 
we  use  for  that  purpose.  Crucibles  of  Au  and  Ag  would  melt  at  high 
temperatures.  But  Pt  is  cheaper  than  Au,  harder  and  more  durable 
than  Ag,  infusible  at  all  temperatures  of  our  furnaces  nnd  is  left 
intact  by  acicls  and  alkaline  carbonates.  Pt  unites  all  the  valuable 
properties  of  Au  and  of  porcelain,  resisting  the  action  of  heat  and  of 
almost  all  chemical  agents.  Without  Pt,  the  composition  of  most 
minerals  would  have  yet  remained  unknown." — Liebig. 


ALLADIUM  :  symbol,  Pd  ;  specific  gravity,  11.4  >  atomic  icciyhl, 
106.3  m.  c. 

4OO.  Palladium. — This  metal  is  contained  in  most 
platinum  "  ores,"  and  is  found  native.  Is  has  a  color  re- 
sem-bling  that  of  platinum.  Its  melting  point  is  about 
that  of  wrought  iron,  the  lowest  of  any  of  the  metals  of 
this  group.  It  possesses  the  power  of  absorbing  hydrogen 
in  a  greater  degree  than  any  other  metal  (§  24,  d).  It  has 
not  been  largely  employed  in  the  arts  although  its  silver- 


312  RHODIUM — IRIDIUM — RUTHENIUM.  §  400 

white  color  and  unalterability  in  the  air  have  led  to  its  use 
in  preparing  the  graduated  surfaces  of  astronomical  instru- 
ments. It  does  not  tarnish  on  exposure  to  hydrogen  sul- 
phide and  has  been,  therefore,  used  for  coating  silver  arti- 
cles and  by  dentists  as  a  substitute  for  gold. 


RHODIUM  :  symbol,  Rh;  specific  gravity,  12.1 ;  atomic  weight, 
104.1  m.  c. 

401.  Rhodium. — This  metal  is  found  in  platinum  "  ore."  It 
has  the  color  and  lustre  of  aluminum.  It  is  melted  with  greater 
difficulty  than  platinum.  It  is  almost  insoluble  in  acids,  but  is  more 
easily  acted  upon  by  chlorine  than  any  other  of  the  platinum  metals. 


IRIDIUM;  symbol,  IT;  specific  gravity,  22.  38  ;  atomic  weight, 
192.7  m.c. 

402.  Iritlium.  —  This  metal  also  is  found  in  platinum 
"  ore."  It  has  a  white  lustre,  resembling  that  of  polished 
steel.  It  is  very  brittle  when  cold  but  slightly  malleable 
at  a  white  heat.  Pure,  massive  iridium  is  not  attacked  by 
aqua  regia.  An  alloy  of  one  part  of  iridium  and  nine  parts 
of  platinum  is  extremely  hard,  as  elastic  as  steel,  more 
difficultly  fusible  than  platinum,  unalterable  in  the  air  and 
susceptible  of  a  beautiful  polish.  This  alloy  was  adopted 
by  the  International  Commission  at  Paris  in  1872  for  the 
standard  metric  measures.  Iridium  is  the  most  -difficultly 
fusible  of  the  platinum  metals  except  ruthenium  and 
osmium.  It  has  been  used  for  the  negative  electrodes  in 
electric  lamps.  ^ 


RUTHENIUM*  :    symbol,  Ru  ;  specific  gravity,  12.26-,   atomic 
weight,  103.5  m.  c. 

403.  Riitlienimii,—  This  metal  is  found  in  platinum  and 
other  ores.  It  combines  with  oxygen  more  readily  than  any  of  the 
other  platinum  metals  except  osmium,  It  is  hard  and  brittle,  and, 


§  404  OSMIUM.  313 

next  to  osmium,  the  most  difficultly  fusible  metal  of  this  group. 
It  is  only  slightly  acted  upon  by  aqua  regia.  It  combines  with 
chlorine  nt  a  white  heat. 


OSMIUM:  symbol,  Os;  specific  gravity,  22477  ;  atomic  weight, 
198.6  m.  c. 

•  l()l.  Osmium.  —  This  metal  is  found  in  platinum  "ore,  "from  the 
other  constituents  of  which  it  is  easily  separated,  as  it  unites  directly 
with  oxygen  to  form  a  very  volatile  compound,  OsO4.  Osmium 
crystals  have  a  bluish  white  color  and  are  harder  than  glass.  Osmium 
is  the  heaviest  known  substance  and  has  not  yet  been  fused.  It  is 
not  used  in  the  arts  but  its  alloy  with  iridium  (osmiridium)  is  used 
for  tipping  gold  pens  as  it  is  not  attacked  by  acids,  and  for  the  bear- 
ings of  the  mariner's  compass  as  it  does  not  oxidize  and  is  non-mag- 
netic. 

Note.  —  Gold,  silver,  platinum,  palladium,  rhodium  and  iridium 
ate  sometimes  called  "  the  noble  metals." 

H-° 


*  -  \      EXERCISES. 

•-•' 

1.  What  takes  place  when  Na  is  thrown  into  H80  ? 

2.  Describe  an  experiment  showing  the  difference  between  a  mix- 
ture and  a  compound..  --vy^ 

3.  State  the  effect  of  heat  upon  Mn02,  KCI03,  NH4CI,  NH4N03,  P 
and  S  respectively. 

4.  You  are  given  Zn,  H2S04,  KHO  and  H20  and  required  to  prepare 
H  from  them  by  two  distinct  processes.    Describe  the  processes  and 
write  the  reaction  for  each.  ^  ^  j^frj    "V  {/  at/j^-5^" 

5.  I  have  two  cylindrical  jars  or  H,  one  of  which  1  hold  mouth 
upward,  the  other  mouth  downward.     At  the  end  of  30  seconds,  I 
plunge  a  lighted  taper  into  each  jar.    Tell  what  you  would  expect  to 
take  place  in  each  case.  *)}-{    tf 

6.  What  are  the  products  of  the  combustion  of  f-f2S  in  the,air. 

7.  How  can  you  make  H2S04  from  S,  H20  and  HN03  ?  5r^T? 

S.  What  elements  can  be  obtained  from  HCI,  NH3  and  H20?    How^; 
would  you  obtain  them  in  each  case  ? 

9.  (a.)  When  H  is  burned  in  air,  what  is  the  product?    (&.)  When 
burned  in  Cl  ? 

10.  An  electric  spark  is  produced  in  a  mixture  of  120  CM.  cm.  of.  H 
and  60  cu.  cm.  of  O.    How  would  you  conduct  the  experiment  so  as 
to  show  the  gaseous  condensation  ? 


314  OSMIUM.  §  404 

, 

11.  You  are  required  to  prepare  0  from  Cl  and  H20.     How  would 
you  do  it  ? 

12.  You  are  given  some  Hg,  a  glass  flask,  a  lamp,  some  glass  tub- 
ing and  required  to  make  pure  0.    How  will  you  do  it  under  ordi- 
nary barometric  conditions  V ' 

13.  When  HN03  is  .poured  on  Cu.  how  does  the  action  differ  from" 
a  simple  solution  ?  (J 

14.  You  are  given  ammonium  carbonate  and  nitric  acid  and  re- 
quired Jo  prepare  laughing  gas  from  the  materials.     How  will  you 
doit?  nt9J^/iov.x  ^^^^fej^f^t. 

15.  What  is  the  fineness  of  British  gold  coin  in  carats?   2.  Q_ 

16.  When  a  positive  monad  radical  replaces  an  atom  of  H  in  NH3, 
/  the  compound  ammonia  is  called  an  amine.     See  §  96,  a.k  Write  the 

typical  symbol  for_di-ethylamine  ;  for  potassamine.  L  /v/. 

17.  When  a  negative  (or  acid)  monad  radical  replaces  fc'n  atom  of 
H  in  NH3,  the  compound  ammonia  is  called  an  amide.    Write  the 
symbol  for  di-iodamide.     The  symbol  for  acetyl  is  given  on  p.  183. 
Write  the  symbol  for  acetamide. 

18.  Write  the  symbols  for  potassium  sulphite  ;  hydrogen  potassiuin 
sulphite  ;  calcium  sulphite  and  hydrogen  calcium  sulphite.  0%^  Jvf  #?  ' 

19.  Write  the  name  and  full  graphic  symbol  for 

^-(S02)-(HO)        '•  -' 

20.  Which  of  the  graphic  symbols  called  for  in  Ex.  5,  p.  227,  is 


preferable?    Why?    See  §  164,  a. 

21.  Write  the  graphic  symbol  for  phosphorus  tetricdide  (P2I4)  in- 
dicating trivalent  P. 

22.  Write    the    graphic    symbol    for    pyrophosplioric    chloride, 

ao  r\     \     J     '    /        /?      />^\  ^  <if  ?-~  2?—  /*  w  &~  /?  *"  O-'  C^  f 
4r2U3.  ^v      *  4/">v         &,\ 

23.  (a.)  Write  *the  graphic  symbol  for  H3P03$4!(&.)  Does  t 
bol  indicate  a  dibasic  or  a  tribasic  acid  ?       4?  -*-  •' 

24.  Explain  the  fact  that  when  new  flannel  is  first  was 
alkaline  soap,  it  becomes  yellow. 

25.  What  weight  of  0  is  needed  to  burn  9  g.  of  CS8  ?'-/7-/-/ '  ^C" 

26.  How  would  you  distinguish  between  Pt  and  Ag?    Between ^.Pt 
and  Sn  ?    Between  Ag  and  Sn  ? 


*h 


1.  Table  of  the  Elements.— An  alphabetical  list  of  the 
elements  with  their  symbols  and  atomic  weights  is  given  below.  In 
the  body  of  the  work  some  of  the  atomic  weights  were  given  in  ap- 
proximate numbers,  for  greater  ease  in  memorizing  and  computation. 
In  the  table  below,  the  atomic  weights  are  given  according  to  the 
most  accurate  determinations  yet  made.  The  less  important  ele- 
ments are  printed  in  italic. 


Name. 
Aluminum. . 


Sym- 
bol. 


Alicro- 
criths. 

27.3 


AL, 

^Antimony  (stibium)..  .Sb  .  .122 

Arsenic As...  74.9 

Barium Ba...l36.8 

Beryllium Be 

(See  Glucinum.) 

Bismuth Bi.  .210 

Boron B....  11 

Bromine Br.  ...79.75 

Cadmium. Cd...lll.6 

Ccesium Cs...l32.5 

^  Calcium Ca...  39.9 

*  Carbon. .,  .  .C. ...  11.97 


Cerium . 


,Ce.. .141.2 


-  -Chlorine Cl...  35.37 

Chromium Cr....  52.4 

Cobalt Co...   58.6 

Columbium Cb .     94 

Copper  (cuprum) Cu.. ,  63 . 1 

Davyum Da.. 153 

Decipium De.  .157 

Didymium Di  . .  147 

Erbium Er  ..169 

Fluorine F...  19.1 

Gallium Ga...  69.8 

Glucinium 

(See  Glucinum.) 
Glucinum Gl.. .  92 


Sym-  Micro* 
ool.    criths. 


Name. 

Qold(aurum) Aul96.2 

-Hydrogen H  . .  1 

Indium In. 113.4 

Iodine I. .126.53 

Iridium Ir  192.7 

Hron Fe..55.9 

Lanthanum. La  139 

Lead  (plumbum) : Pb  206.4 

Lithium Li  . . 7.01 

Magnesium Mg.  23.98 

Manganese Mn..54.8 

Mercury  (Jiydrargyrum).  Hgl99.8 

Molybdenum Mo. 95.8 

Nickel Ni.  58.6 

Niobium  (See  Columbium).  Mb 

"Nitrogen N  . .  14.01 

Norwegium No.  72. 

Osmium Os  198  6 

•Oxygen 0  ..15.96 

Palladium Pd  106.2 

-.Phosphorus P  .  .30.96 

Platinum Pt.196.7 

•4  Potassium  (tedium).  ...  K  ..  39.04 

j  Rhodium Rh.104.1 

I  Rubidium Rb..85.2 

!  Ruthenium Ru.103.5 

Selenium Se.-79 

..  (See  Silicon.)...  SI 


316 


APPENDIX. 


Micro- 


Silicon  ................  Si  ____  28 

Silver  (argentum)  ......  Agl07.66 

K  Sodium  (natrium)  ......  N  a.  22.  29 

Strontium  .............  Sr  .  .87.2 

^Sulphur  ...............  S.  ..31.98 

Tantalum  ..............  Tal82 

Tellurium  ............  Te  128 

Terbium  ..............  Tr..99 

Thallium.  .  .Tl.203.6 


Thorium Th.231.5 

Tin  (stannum) Sn.117.8 

Titanium Ti  .  .48.15 

Tungsten  (wolframium)  W.  183.5 

Uranium U  r.240 

Vanadium V..   51.2 

Yttrium Yt...92.5 

Zinc Zn...64.9 

Zirconium Zr. .  90 


2.  Iflctric  Pleasures. — For  a  fuller  consideration  of 
tlie  international  or  metric  measures,  the  pupil  is  referred  to 
Avery's  Natural  Philosophy,  §§  24-30  and  35-36.  Chemists 
of  all  countries  use  these  units,  almost  exclusively.  The  deci- 
meter rule  (Fig.  122)  is  shown  as  being  divided  into  ten  cen- 
timeters, each  of  which  is  divided  into  ten  millimeters.  The 
cubic  decimeter  measures  a  volume  called  a  liter  (pronounced 
leeter).  The  cubic  centimeter  (cu.  cm)  is  0.001  of  a  liter  (I). 
The  weight  of  one  cu.  cm.  of  water  at  the  freezing  tempera- 
ture is  a  gram  (g).  These  three  units,  the  liter,  the  cubic 
centimeter  and  the  gram  are  the  ones  of  most  frequent  occur- 
rence in  chemical  works.  The  actual  weights  and  measures 
should  be  habitually  used  in  every  school  laboratory. 


1  cu.  in.  =16.386  cu.cm.  I  grain =0.0648  g.  jf 
x  „,*,„_ w.v^,  «„«,.  1  liquid  qt.=0.946  I.  loz. Troy  =31.1035.?.  | 
1  yard=0.9144wJl  fl'd  oz.= 29.562  ^.m.|llb.Av.= 0.4535^.  J 

3.  Thermometers. — Chemists  use  the  cen-  a 
tigrade  thermometer  almost  exclusively.     One  or  2- 
more  centigrade  thermometers  (chemical),  having  s. 
the  scale  marked  on  the  glass  tube,  and  having  no  Z 
frame  like  that  of  the  ordinary  hous3  thermometer,  j] 
should  be  in  every  school  laboratory.     In  this  book  fi 
temperatures  are  always  given  in  centigrade  do-  "5- 
grees.     To  change  centigrade  readings  to  Fahren-  §• 
heit  readings,  multiply  the  number  of  centigrade  -w 
degrees  by  f  and  add  32.     To  change  Fahrenheit 
readings  to  centigrade  readings,  subtract  32  from 
the  number  of  Fahrenheit  degrees  and  multiply 
the  remainder  by  f.    (See  Ph.,  §§  480,  481.) 

The  best  thermometers  are  straight  glass  tubes, 
of  uniform  diameter,  with  cylindrical  instead  of 
spherical  bulbs ;   such  instruments   can  be  passed  tightly 
^   **     through  a  cork,  and  are  free  from  many  liabilities  to  error 
FIG.  123  to  which  thermometers  with  paper  or  metal   scales  are 


APPENDIX.  317 

always  exposed.  A  cheaper  kind  of  thermometer,  having  a  paper 
scale  enclosed  in  a  glass  envelope,  will  answer  for  most  experiments. 

4.  Gla§§  Working.  —Much  of  the  chemist's  apparatus  is 
made  of  glass  which  softens  and  becomes  plastic  when  heated.  Skill- 
ful workers  in  wood  or  metal  may  be  found  in  almost  any  town,  but 
glass  working  will  generally  devolve  upon  the  teacher  and  pupil. 
It  is,  therefore,  discussed  at  some  length  in  this  place. 

(a.)  Glass  Tubing.—  Glass  tubes  bent  into  various  shapes  are  con- 
stantly needed.  The  pupil  should  acquire  dexterity  in  preparing 
these  for  himself.  Glass  tubing  is  of  two  qualities,  hard  and  soft. 
The  former  softens  with  difficulty  and  is  desirable  only  for  ignition 
or  combustion  tubes.  (Fig.  18.)  But  little  of  it  will  be  needed.  It 
is  generally  better  to  buy  the  ignition  tubes  required.  Soft  glass 
tubing  will  be  needed  in  larger  quantities.  In  purchasing,  it  is  re- 
commended that  the  greater  part  be  of  a  single  size.  Fig.  124  shows 
desirable  sizes  and  the  proper  thickness  of  the 
glass  for  each  size.  By  using,  habitually,  one 
given  size  of  tubing,  the  various  articles  made 
therefrom  are  more  easily  interchangeable  than  FIG.  124. 

they  would  otherwise  be. 

(&.)  Cutting  and  Bending  Tubes. — Glass  tubing  and  rods  must  gen- 
erally be  cut  the  desired 
length.  For  this  purpose, 
lay  the  tube  or  rod  upon 
the  table  and  make  a 
scratch  at  the  required  dis- 
tance from  one  end  with 
a  three-cornered  file.  Hold 

P  the  tubing  in  both  hands, 

as  shown  in  Fig.  125,  with 

the  scratch  away  from  you  and  the  two  thumbs  opposite  the  mark. 
With  a  sharp  jerk,  push  out  the  thumbs  and  pull  back  the  fingers. 
The  glass  will  snap  squarely  off  at  the  desired  place.  The  best  flame 
for  bending  ordinary  tubes  is  that  of  a  fish-tail  gas  burner,  but  that 
of  a  spirit  lamp  will  do.  Be  sure  that  the  tube  is  dry  ;  do  not 
breathe  into  it  before  heating  it.  Bring  the  part  of  the  tube  where 
the  bend  is  desired  into  the  hot  air  above  the  flame  ;  when  it  is 
thoroughly  warm,  bring  it  into  the  flame  itself.  Heat  about  an  inch 
of  the  tube,  holding  it  with  both  hands  and  turning  it  constantly 
that  it  may  be  heated  uniformly  on  all  sides.  The  tube  should  be 
held  between  the  thumb  and  first  two  fingers  of  each  hand,  the  hands 
being  below  the  tube,  palms  upward  and  the  lamp  between  the  hands. 
The  desired  yielding  condition  of  the  glass  will  be  detected  by  feel- 


318 


APPENDIX. 


ing  better  than  by  seeing,  i.  «.,  the  fingers  will  detect  the  yielding 
of  the  glass  before  the  eye  notices  any  change  of  color  or  form. 
i  When  the  glass  yields 

easily,  remove  it  from  the 
flame  and  gently  bend  the 
ends  from  you.  If  the 
concave  side  of  the  g'*ass  be 
too  hot,  it,  will  "  buckle  ;  " 
if  the  .convex  side  be 
too  hot,  the  curve  will 
be  flattened  and  its  chan- 
nel contracted.  Practice, 
and  practice  only,  will 
enable  you  to  bend  a  tube 
neatly.  When  a  tube  or 
rod  is  to  be  bent  or  drawn 
near  its  end,  a  temporary 
handle  may  be  attached  to 
FIG.  126.  it  by  softening  the  end  of 

the  tube  or  rod,  and  pressing  against  the  soft  glass  a  fragment  of 
glass  tube,  which  will  adhere  strongly  to  the  softened  end.  This 
handle  may  subsequently  be  removed  by  a  slight  blow  or  by  the  aid 
of  a  file.  If  a  considerable  bend  is  to  be  made,  so  that  the  angle 
between  the  arms  will  be  very  small  or  nothing,  as  in  a  siphon,  the 
curvature  can  not  be  well  produced  at  one  place  in  the  tube,  but 
should  be  made  by  heating,  progressively,  several  cm.  of 
the  tube,  and  banding  continuously  from  one  end  of  the 
heated  portion  to  the  other  (Fig.  127).  The  several  parts 
of  such  a  bent  tube  should  all  lie  in  the  same  plane  so 
that  the  finished  tube  may  lie  flat  on  a  level  surface.  It 
is  difficult  to  bend  tubing  large  enough  for  TJ-tubes 
(Fig.  14).  They  would  better  be  bought.  When  the  end 
of  a  tube  or  rod  is  to  be  heated,  it  is  best  to  begin  heating 
the  glass  about  2  cm.  from  the  end,  as  cracks  start  easily 
from  an  edge.  Smooth  the  sharp  edges  at  the  ends  of  the 
tube  by  heating  them  to  redness.  Anneal  the  bent  tube  by  with- 
drawing it  very  gradually  from  the  flame  so  as  not  to  let  it  cool 
suddenly.  Never  lay  a  hot  tube  on  the  bench  but  put  it  on  some 
poor  conductor  of  heat  until  it  is  cool.  Gradual  heating  and  gradual 
cooling  are  alike  necessary.  Glass  tubing  may  be  advantageously 
united  by  rubber  or  caoutchouc  tubing  when  the  substance  to  be 
conducted  will  not  corrode  the  latter,  or  when  the  temperature  em- 
ployed is  not  too  high.  Short  pieces  of  rubber  tubing  are  much  used 


APPENDIX.  319 

as  connectors  to  make  flexible  joints  in  apparatus.  Gas  delivery 
tubes,  etc.  (Fig.  6),  are  generally  made  in  several  pieces  joined  with 
caoutchouc  connectors,  which,  by  their  flexibility,  add  much  to  the 
durability  of  the  apparatus.  Long  glass  tubes  bent  several  times 
and  connecting  heavier  pieces  of  apparatus  are  almost  sure  to  break, 
even  with  careful  use.  The  internal  diameter  of  the  connector 
should  be  a  little  less  than  the  external  diameter  of  the  glass 
tubing.  The  connection  may  be  made  more  easily  by  wetting  the 


(c.)  Drawing  Tubes. — In  order  to  draw  a  glass  tube  down  to  a  finer 
bore,  thoroughly  soften  it  on  all  sides  uniformly  for  1  or  2  cm.  of  its 
length  and  then,  taking  the  glass  from  the  flame,  pull  the  parts 
asunder  by  a  cautious  movement* of  the  hands.  The  length  and 
fineness  of  the  drawn  out  tube  will  depend  upon  the  length  of  tube 
heated  and  the  rapidity  of  motion  of  the  hands.  If  the  drawn  out 
part  of  the  tube  is  to  have  thicker  walls  in  proportion  to  its  bore 


FIG.  128. 

than  the  original  tube,  keep  the  heated  portion  soft  for  two  or  three 
minutes  before  drawing  out  the  tube,  pressing  the  parts  slightly 
together  the  while.  By  this  process  the  glass  will  be  thickened  at 
the  hot  ring.  By  cutting  the  neck  at  a,  with  a  file,  jets  are  formed 
such  as  are  needed  for  Exps.  21,  26,  etc. 

(d.)  Closing  Tubes. — Take  a  piece  of  tubing  long  enough  to  make 
two  closed  tubes  of  the  desired  length.  Heat  a  narrow  ring  at  the 
middle  of  the  tube  and  draw  it  out  slightly.  Direct  the  point  of  the 
flame  upon  the  point  c  (Fig.  128)  which  is  to  become  the  bottom  of 
one  tube,  draw  out  the  heated  part  and  melt  it  off.  Each  half  of  the 
original  tube  is  now  closed  at  one  end  but  they  are  of  different  forms. 
(Fig.  129.)  You  can  not  close  both  ends  satisfactorily  at  the  same 
time.  A  superfluous  knob  of  glass 
generally  remains  upon  the  end.  If 
FIG.  129.  small,  it  may  be  removed  by  heating 

the  whole  end  of  the  tube,  and  blowing  moderately  into  the  open 
end.  The  knob  being  hotter  than  any  other  part,  yields  to  the  pres- 
sure from  within  and  disappears.  If  the  knob  is  large,  it  may  be 
drawn  off  by  sticking  to  it  a  fragment  of  tube,  and  then  softening 
the  glass  above  the  junction.  The  same  process  may  be  applied  to 


320  APPENDIX. 

the  too  pointed  end  of  the  right  hand  half  of  the  original  tube,  or  to 
any  bit  of  tube  that  is  too  short  to  make  two  closed  tubes.  When 
the  closed  end  of  a  tube  is  too  thin,  it  may  bs  strengthened  by  keep- 
ing the  whole  end  at  a  red  heat  for  two  or  three  minutes,  turning 
the  tube  constantly  between  the  fingers.  In  all  of  these  processes, 
keep  the  tube  in  constant  rotation  that  it  may  be  heated  on  all  sides 
alike.  It  will  be  difficult  for  the  pupil  satisfactorily  to  work  tubing 
large  enough  for  test  tubes  (Fig.  7).  They  would  better  be  bought. 
They  come  in  nests  of  assorted  sizes. 

(e.)  Blowing  Bulbs.— This  is  a  more  delicate  operation  than  any  yet 
described.  It  requires  considerable  practice  to  secure  even  moderate 
success.  If  the  bulb  is  to  be  large  compared  with  the  size  of  the  tube 
carrying  it,  the  glass  must  be  thiqjiened  before  the  bulb  can  be  blown. 
If  the  bulb  is  to  be  at  the  middle  of  a  piece  of  tubing,  the  tube  is  to 
be  heated  red  hot  at  that  place,  removed  from  the  flame,  and  the  ends 
gently  pressed  toward  each  other.  If  the  glass  "  wrinkles  "  in  thick- 
ening, as  it  may  do  if  tooliighly  heated,  a  good  bulb  cannot  be  blown 
there.  If  the  bulb  is  to  be  at  the  end  of  the  tube,  the  end  is  closed 
and  the  glass  then  thickened  by  holding  the  closed  end  in  the  flame, 
keeping  it  in  constant  rotation.  When  the  glass  is  so  soft  that  it 
bends  from  its  own  weight,  the  end  of  the  tube  is  placed  between 
the  lips,  the  other  end,  if  open,  is  closed  with  the  finger,  and  air  is 
steadily  pressed  into  the  tube  by  the  mouth  rather  than  by  the  lungs, 
the  tube  being  kept  in  rotation.  This  must  be  done  quickly  but 
cautiously,  the  eye  being  kept  upon  the  heated  part.  Practice  will 
soon  enable  you  to  determine  when  to  stop  the  pressure.  If  the  bulb 
thus  obtained  be  not  large  enough,  it  may  be  reheated  and  again  ex- 
panded, provided  the  glass  be  thick  enough.  The  pressure  must  not 
be  too  strong  or  sudden  and  never  applied  while  the  glass  is  in  the 
flame.  It  is  better,  as  a  general  thing,  to  buy  funnel. tubes  (Fig.  6) 
and  bulb  tubes  (Fig.  16)  than  to  make  them. 

(/.)  Welding  Glass  Tubes. — The  well  fitted  ends  of  two  pieces  of 
glass  tubing  may  be  joined  by  heating  them  to  redness  and  press- 
ing them  together  while  in  a  plastic  condition.  Practice  is  necessary 
to  good  results,  but  the  skill  should  be  acquired  as  funnel  tubes  and 
other  pieces  of  apparatus  often  need  mending.  If  necessary,  the  end 
of  one  tube  may  be  enlarged  by  rapidly  turning  the  glass  in  the  flame 
until  it  is  highly  heated,  and  then,  while  it  is  still  in  the  flame,  flaring 
it  outward  with  an  iron  rod.  Hold  the  ends  together  and  heat  them 
well  with  a  pointed  flame,  until  they  are  united  all  around.  Force 
air  in  at  one  end  to  swell  out  the  joint  a  little,  heat  it  again  until  the 
swelling  sinks  in,  blow  it  out  again,  and  repeat  the  process  until  the 


APPENDIX.  321 

joint  is  smooth  and  the  pieces  well  fused  into  each  other.  Without 
this  repeated  heating  and  blowing  out,  the  joint  is  likely  to  crack 
open  when  cooled. 

(g. )  Piercing  Tubes. — A  hole  may  be  made  in  the  side  of  a  tube 
or  other  thin  glass  apparatus  by  directing  a  pointed  blowpipe  flame 
upon  the  glass  until  a  spot  is  red  hot,  closing  the  other  end,  if  open, 
with  the  finger  and  bio  wing  forcibly  into  the  open  end.  The  glass  is 
blown  out  at  the  heated  spot.  The  edge  may  be  strengthened  by 
laying  on  a  thread  of  glass  around  it,  and  fusing  the  thread  to  the 
tube  in  the  blowpipe  flame. 

(h.)  Glass  Cutting  and  Cracking,  etc. — For  cutting  glass  plates,  a 
glazier's  diamond  is  desirable  but  efficient  and  cheap"  glass-cutters," 
made  of  hardened  steal  have  been  put  upon  the  market  within  a  few 
years.  For  shaping  broken  flasks,  retorts  and  other  pieces  of  thin 
glassware,  cracking  is  more  satisfactory.  A  scratch  is  made  with  a 
file,  preferably  at  the  edge  of  the  glass.  Apply  a  pointed  piece  of 
glowing  charcoal,  a  fine  pointed  flame  or  a  heated  glass  or  metal  rod 
to  this  scratch.  The  sudden  expansion  by  heat  will  generally  pro- 
duce a  crack.  If  the  heat  does  not  make  one,  touch  the  hot  spot  with 
a  wet  stick.  A  crack  thus  started  may  be  led  in  any  desired  direc- 
tion by  keeping  the  heated  rod  or  fine  flame  moving  slowly  a  few  mm. 
in  front  of  it  as  it  advances. 

A  flask  or  retort  neck  may  sometimes  be  cracked  round  by  tying  a 
string  soaked  in  aloohol  or  turpentine  round  the  place,  setting  fire  to 
the  string  and  keeping  the  flask  turning.  When  the  string  has 
burnt  out,  invert  the  flask  and  plunge  it  into  water  up  to  the  heated 
circle.  It  will  generally  crack  as  desired. 

The  lower  ends  of  glass  funnels,  and  the  ends  of  gas  delivery 
tubes  that  enter  the  generating  bottle  or 
flask  should  be  ground  off  obliquely  on 
a  wet  grindstone,  or  shaped  thus  with  a 
file  wet  with  a  solution  of  camphor  in 
turpentine,  to  facilitate  the  dropping  of 
liquids  from  such  extremities.  With  a 
little  care  and  patience,  a  hole  may  be 
drilled  through  glass  by  using  a  file  kept 
wet  with  the  solution  mentioned.  Such 
a  hole  may  easily  be  enlarged  or  given 
any  desired  shape  with  a  file  thus  wet.  FIG.  130. 

The  lips  of  bottles  may  be  ground  flat  by  rubbing  them  on  a  flat 
surface  sprinkled  with  emery  powder  kept  wet.  The  bottle  should 
be  grasped  by  the  neck  and  rubbed  around  with  a  gyratory  motion, 


322 


APPENDIX. 


pains  being  taken  to  prevent  a  rocking  motion  whereby  first  one  side 
of  the  lip  shall  be  ground  and  then  another,  thus  leaving  the  bottle 
in  as  bad  a  condition  at  the  end  of  the  work  as  at  the  beginning. 
The  work  may  be  finished  by  rubbing  with  fine  emery  powder  on  a 
piece  of  plate  or  window  glass,  until  all  parts  of  the  ground  surface 
lie  in  the  same  plane.  See  F  rick's  Physical  Technics  [17]. 


FIG.  131. 


FIG.  132. 


FIG.  133. 


5.  Pipettes  and  Graduates. — Tubes  drawn  out  to  a  small 
opening  at  one  end  and  used  to  remove  a  small 
quantity  of  a  liquid  from  a  vessel  without  dis- 
turbing the  bulk  of  its  contents,  are  called 
pipettes.  They  often  carry  a  bulb  or  cylindrical 
enlargement,  as  appears  in  the  forms  shown  in 
Fig.  131.  The  manner  of  using  them  is  shown 
in  Fig.  132.  They  are  often  graduated.  A 
cylindrical  measuring  glass,  graduated  to  cubic 
centimeters  (Fig.  133)  is  almost  indispensable  in 
the  laboratory. 

6.  W  oil  life  Bottles.— A  very  conven- 
ient substitute  for  Woulffe  bottles  may  be  made 
by  perforating  the  glass  cover  of  a  fruit  jar  ac- 
cording to  directions  given  in  App.  4,  h.  The 
holes  carry  cork  or  caoutchouc  stoppers  through 
which  the  several  tubes  pass,  as  shown  in 

FIG.  ,34.  Fi«'  134 


APPENDIX.  323 

7.  Thin  Bottomed  Glassware.— Glass  vessels  are  largely 
used  for  heating  liquids  ID  the  laboratory.  All  such  vessels  have 
uniformly  thin  bottoms  that  they  may  not  be  broken  by  unequal  ex- 
pansion when  heated.  If  moisture  from  the  atmosphere  or  other 
source  accumulates  on  the  outer  surface,  it  should  be  carefully  wiped 
off  before  or  during  the  heating. 

Retorts  are  often  used.  Those  that  have  tubulures  (Fig.  37,  a)  are 
preferable  to  those  that  have  not  (Fig.  43).  v 

Florence  Flasks  are  now  much  used  instead  of  retorts  as  they  cost 
much  less.  They  may  be  bought  in  any  size  desired  and  with  the 
bottom  rounded  or  flattened.  (See  Figs.  13,  32,  37?-,  50,  etc.)  Heated 
retorts  and  flasks  should  not  be  placed  on  the  table  as  the  sudden 
cooling  may  break  them.  They  may  better  be  placed  on  rings 
covered  with  listing  or  made  of  straw  or  other  poor  conductor  of 
heat,  as  shown  in  Figs.  43  and  71. 

Beakers  are  thin,  flat-bottomed  glasses  with  slightly  flaring  rims, 
as  shown  in  Figs,  9,  58,  etc.  They  are  conveniently  used  for  heating 
liquids  when  it  is  desirable  to  reach  every  part  of  the  vessel  as  with 
a  stirring  rod.  They  are  generally  sold  in  nests  of  different  sizes. 
Beakers  of  more  than  a  liter's  capacity  are  too  fragile  to  be  desirable. 
Test  Tubes  are  thin  glass  cylinders,  closed  at  one  end  and  having 
lips  slightly  flared.  The  mouth  should  be  of  such  a  size  that  it  may 
be  closed  by  the  ball  of  the  thumb.  The  tube  may  be  held  in  the 
flame  with  the  fingers,  with  wooden  nippers,  as  in  Fig.  2,  or  by  a 
band  of  folded  paper  around  the  upper  end.  A  test  tube  rack,  some- 
what similar  to  the  one  shown 
in  Fig.  135,  should  be  made  or 
bought,  to  hold  the  tubes  upright 
when  in  use  and  to  hold  them 
inverted  when  not  in  use. 

Test  tubes  may  be  held  in  an 
inverted  position,  as  at  the  pneu- 
matic  trough  or  water  pan,  by 

weighting  them  with  lead  rings  cut  with  a  saw  from  lead  pipe.  The 
ring  should  be  of  such  a  size  that  it  will  easily  slip  over  the  tube 
but  not  over  the  lip  of  the  tube.  Test  tubes  may  be  easily  cleaned 
with  little  cylindrical  brushes  made  of  bristles  held  between  twisted 
wires.  They  cost  but  a  few  cents  each.  The  chief  danger  in  clean- 
ing a  test  tube  is  that  the  bottom  may  be  broken  out.  The  brush 
should,  therefore,  have  a  tuft  of  bristles  at  its  end.  When  the  upper 
end  of  a  tube  is  held  in  the  fingers  during  the  heating,  the  tube  should 
be  rolled  or  turned  in  the  flame  so  that  all  sides  may  be'equally  heated. 


324 


APPENDIX. 


8.  Filtering. — Funnels  that  have  an  angle  of  exactly  60°  should 

be  chosen.  The  circular  piece  of  filter  paper  should  be  folded  first 
on  its  diameter,  then  again  at  right-angles 
to  the  first  fold  and  then  opened  out  so  as 
to  leave  three  folds  on  one  side  and  one  on 
the  other,  as  shown  in  Fig.  136.  It  is  then 
to  be  placed  in  a  funnel,  the  funnel  placed 
in  proper  position  and  the  liquid  to  be  fil- 
tered carefully  poured  upon  the  paper.  If 
the  first  filtration  does  not  clear  the  liquid, 
the  filtrate  should  be  poured  back  upon  the 
same  filter  for  refiltration.  Another  way  of 

folding  the  filter  paper  is  to  make  the  first  fold  as  above.     Then  a 

fold  equal  to  a  quarter  of  the  semicircle  is  made  upon  each  side  of 

the  paper.     Each  of  these  smaller  folds  is  then 

folded  back  upon  itself.     The  sheet  is  then  opened, 

as  shown  in  Fig.  137,  and  thus  placed  in  the  fun- 

<L.  nel. 

^1  >^*  ^X^.  Rapid  filtration  may  be 
secured  by  making  a  rib- 
bed filter  as  follows :  Fold 

£*  i ^L |/»  the  paper  as  before  on 

two  diameters  at  right- 
angles    to    each    other. 


FIG.  136. 


FIG.  137. 


FIG.  138. 

Open  at  the  last  fold  and  spread  out  the  paper,  ace,  which  will  have 
a  crease,  co.  Bring  the  corners  a  and  e  to  the  point  c  and  make  the 
creased  lines,  bo  and  do,  so  that  the  paper  shall  be  creased  in  the 
same  way  at  bo,  co  and  do.  Open  the  paper  as  shown  in  Fig.  138, 
and  fold  the  corner  a  upon  b,  creasing  the  paper  in  the  opposite  di- 
rection. Make  similar  creases  midway  between  6  and  c,  between 
c  and  d,  and  between  d  and  e.  The  last  four  folds  leave  creases  op- 
posite in  direction  to  those  made  at  bo,  co  and  do.  On  opening  the 
paper  and  putting  it  into  the  funnel,  it  will  stand  out  from  the  glass, 
touching  it  only  at  several  of  the  edges  of  the  folds. 

Filters  may  be  folded  at  leisure  moments  and  kept  ready  for  use. 

For  coarse  and  rapid  filtering,  the  neck  of  the  funnel  may  be 
plugged  with  tow  or  cotton.  For  filtering  solutions  that  would 
destroy  the  texture  of  the  filter  paper,  a  plug  of  asbestos  or  of  gun 
cotton  is  placed  in  the  neck  of  the  funnel. 

The  funnel  may  be  supported  in  any  convenient  way.  Sometimes 
it  may  be  placed  in  the  neck  of  the  bottle  (Fig.  79),  care  being  had 
that  it  does  not  fit  air  tight.  It  may  often  be  supported  from,  the 
retort  stand  or  other  independent  support.  When  convenient,  the 


APPENDIX. 


325 


lower  end  of  the  funnel  should  touch  the  side  of  the  vessel  that  re- 
ceives the  filtrate  so  that  the  latter  shall  fall  quietly  rather  than  in 
splashing  drops.  The  end  of  the  funnel  neck  should  be  ground  off 
obliquely,  as  stated  in  A  pp.  4,  h. 

When  a  precipitate  has  been  collected  upon  a  filter,  it  may  be 
washed  by  filling  the  filter  two  or  three  times  with 
distilled  water  and  allowing  it  to  run  through.  A 
washing  bottle  (Fig.  139)  is  of  great  convenience,  the 
stream  of  water  being  driven  out  at  c  by  air  from  the 
lungs  forced  in  at  a.  The  stream  of  water  is  directed 
so  as  to  wash  the  precipitate  from  the  sides  of  the 
filter  toward  its  apex.  The  jet  may  be  carried  by  a 
piece  of  flexible  tubing  attached  to  c,  so  that  it  may 
be  turned  in  any  direction  without  moving  the  bottle. 
When  a  precipitate  is  very  heavy,  it  may  be  washed 
by  shaking  it  up  with  successive  quantities  of  water 
in  a  test  tube,  and  pouring  off  the  water  when  the 
precipitate  has  settled  down.  A  wet  glass  rod  held  against  the  lip- 
of  the  test  tube  greatly  assists  in  pouring  off  the  liquid  without  dis- 
turbing the  precipitate. 

9.  Cork*,  etc. — It  is  not  always  easy  to  obtain  corks  of  good 
quality  and  considerable  size.  Many  experiments  have  failed  through 
defects  in  corks  used.  Use  bottles  with  small  mouths  when  you  can. 
Choose  corks  cut  across  the  grain  rather  than  those  cut  with  the 
grain,  as  the  latter  often  provide  continuous  channels  for  the  escape 
of  gases.  Select  those  that  are  as  fine  grained  as  you  can  get.  They 
will  generally  need  to  be  softened  before  use.  This  may  be  done  by 
rolling  on  the  floor  with  the  foot,  on  the  table  with  a  board  or  with  a 
cork  squeezer  made  for  that  purpose.  Corks  may  be  made  less  porous 
by  holding  them,  for  a  few  minutes,  under  the  surface  of  melted 
paraffine  wax. 


FIG.  139. 


FIG.  140. 
In  boring  holes  through  corks,  a  small  knife  blade  or  rat-tail  file 


326  APPENDIX. 

may  be  used,  but  a  set  of  brass  cylinders,  made  for  the  purpose,  is 
more  convenient.  Such  a  set  of  cork  borers  and  the  way  of  using 
them  are  shown  in  Fig.  140.  Use  a  borer  with  a  diameter  a  little 
less  than  that  of  the  glass  tubing  to  be  used.  When  the  borer  be- 
comes dull,  grind  or  file  the  outer  bevelled  edge  and.  with  a  sharp 
knife  blade,  pare  off  the  rough  metal  on  the  inside  of  the  edge. 

Caoutchouc  stoppers  are  more  durable  than  cork  and  much  to  be 
preferred.  They  may  be  bored  as  above  described.  If  they  harden, 
they  may  be  softened  by  being  kept  for  a  time  in  a  closed  flask  con- 
taining a  few  drops  of  turpentine.  If  the  glass  tube  enters  the  bored 
stopper  with  much  difficulty,  wet  the  outside  of  the  tube  with  tur- 
pentine. 

In  passing  glass  tubes  through  stoppers  of  cork  or  caoutchouc,  see 
that  the  end  of  the  tube  is  smooth  (see  App.  4,  &),  hold  the  tube  as 
near  as  possible  to  the  stopper  and  force  it  in  with  a  slow,  steady, 
rotary,  onward  motion.  Do  not  hold  a  funnel  tube  by  the  funnel,  or 
a  bent  tube  at  the  bend  if  you  can  avoid  doing  so.  If  the  glass  tube 
enters  the  bored  cork  with  much  difficulty,  smear  the  outside  of  the 
tube  with  soap  and  water.  Test  all  joints  made,  in  the  manner  de- 
scribed in  §  21. 

The  sticking  of  glass  stoppers  is  a  frequent  source  of  trouble  in  the 
laboratory.  Many  methods  of  loosening  them  have  been  suggested. 
When  one  fails  another  must  be  tried.  Under  such  circumstances, 
patience  and  persistence  are  necessary.  It  is  hardly  ever  necessary 
to  break  the  bottle.  Generally,  the  stopper  may  be  started  by  tap- 
ping it  lightly  on  opposite  sides  alternately  with  a  block  of  soft  wood. 
The  expansion  of  the  bottle  neck  by  heat  will  often  loosen  the  stopper. 
The  heat  may  be  applied  by  friction  with  the  fingers  or  a  piece  of  tape, 
by  a  flame  or  by  hot  water.  If  the  application  of  heat  be  continued 
too  Ion <r,  the  stopper  will  expand  as  well  as  the  neck,  and  the  trial 
end  in  failure.  As  a  last  resort,  fit  two  pieces  of  soft  wood  between 
the  lip  of  the  bottle  and  the  lower  side  of  the  projecting  part  of 
the  stopper.  Tie  them  firmly  in  place  and  soak  in  water  for  several 
hours.  If  the  wood  does  not  swell  enough  to  start  the  stopper,  pour 
hot  water  over  the  wooden  pieces,  and  the  trouble  will  generally  be 
at  an  end. 

When  you  pour  a  liquid  from  a  bottle,  as  into  a  test  tube,  hold  the 
bottle  in  the  right  hand  with  the  label  toward  the  palm.  Remove  the 
stopper  with  the  little  finger  or  with  the  third  and  fourth  fingers  of 
the  left  hand,  the  thumb  and  forefinger  of  which  may  hold  the  test 
tube.  Remove  the  liquid  drop  that  adheres  to  the  lip  of  the  bottle 
by  touching  it  with  the  stopper,  replace  the  stopper  and  return  the 
bottle  to  its  proper  place.  It  is  seldom  necessary  to  place  either 


APPENDIX, 


327 


stopper  or  bottle  on  the  table.  In  a  little  while  you  will  acquire 
the  habit  of  doing  these  things  in  this  way  and  thus  avoid  much 
annoyance. 

1O.  Stands,  Supports,  Bullis,  etc.  —  Flasks,  etc.,  are 
often  supported  over  the  lamp  by  a  retort  stand,  as  shown  in  Figs. 
37  and  38.  This  stand  has  a  heavy  base  and  several  movable  iron 
rings  of  graduated  sizes  secured  to  the  vertical  rod  by  binding  screws. 
Glass  vessels  thus  supported  are  well  protected  from  the  direct  flame 
of  the  lamp  by  a  piece  of  wire  gauze,  as  shown  in  Fig.  37.  Oc- 
casionally, a  very  gradual  and  even  heating  is  desired.  Under  such 
circumstances,  the  wire  gauze  may  be  replaced  by  a  sand  bath,  which 
consists  of  a  shallow  pan,  beaten  out  of  sheet  iron  and  filled  with 
sand,  as  shown  in  Fig.  42.  Sometimes, 
it  is  desirable  to  heat  a  vessel  moder- 
ately, keeping  it  continuously  below  a 
certain  temperature.  This  may  be  ac- 
complished by  placing  the  vessel  in  an- 
other vessel  partly  filled  with  water  and 
heating  the  water,  as  shown  in  Fig.  89. 
Copper  cups  with  tops  made  of  concen- 
tric rings  that  may  be  adapted  to  the 
size  of  the  vessel  are  offered  for  sale. 
A  good  enough  water  bath  may  be  made 
of  an  old  tinned  fruit  can.  Care  should 
be  had  that  the  water  of  the  bath  is  not 
allowed  to  boil  away.  Fig.  141  shows 
various  clamps  and  fittings  for  a  retort 
stand,  by  means  of  which  tubes,  flasks, 
retorts,  etc.,  are  easily  held  in  any  de- 
sired position.  See  Fig.  37.  Many 
convenient  supports  may  be  made  with 
corks  and  glass  rods  stuck  on  invert3d 
funnels.  A  convenient  support  for  a 
small  vessel  may  be  made  in  the  form 
of  an  equilateral  triangle  by  twisting  FIG.  Al- 

together three  pieces  of  soft  iron  wire  at  the  cor- 
ners, as  shown  in  Fig.  142.  Each  of  the  wires 
may  be  run  through  the  stem  of  an  ordinary  clay 
pipe.  The  support  may  be  placed  upon  the  ring 
of  a  retort  stand  or  held  by  a  cork  into  which, 
the  twisted  wires  at  one  corner  have  been  thrust. 
A  convenient  support  for  test  tubes,  etc.,  may  be 
made  by  binding  the  middle  part  of  a  copper 


FIG.  142. 


3*8 


to 


FIG.  143. 
be  removed. 


wire,  1  or  2  mm.  in  diameter,  about  a  stout  cork.  The  free  ends  of 
the  easily  flexible  wire  may  be  wound  spirally  around  the  test  tube. 
The  cork  serves  as  a  handle  ;  if  perforated,  it  may  be  placed  upon 
the  rod  of  the  retort  stand.  The  wire  may  be  bent  so  as  to  place  the 
tube  in  any  desired  position. 

11.  Ulortars,— A  mortar  is  a  vessel,  m,  in  which  solid  sub- 
stances may  be  powdered  with  a  pestle,  i.  They 
are  made  of  iron,  porcelain,  agate,  etc.  Porcelain 
mortars' of  the  best  quality  are  made  of  "  Wedge- 
wood  ;  "  they  are  unglazed,  should  not  be  suddenly 
heated  and  may  be  cleaned  by  rubbing  with  sand 
wet  with  nitric  or  sulphuric  acid  or  caustic  potash 
or  soda,  according  to  the  nature  of  the  substance 
Agate  mortars  are 
very  small  and  expensive.  In  many 
cases,  a  stout  bowl  will  answer  as  a 
mortar,  while  a  pestle  may  be  made  of 
hard  wood.  Many  substances  may  be 
powdered  on  a  hard  surface  by  the  use 
of  a  rolling  pin,  like  that  used  by  a 
pastry  cook,  or  by  rolling  a  stout  bot- 
tle over  them.  If  a  solid  is  to  be 
broken  by  blows  preparatory  to  powder- 
ing, an  iron  mortar  and  pestle  are  de- 
sirable. The  pestle  may  be  worked  FIG.  144. 
through  a  hole  in  a  pasteboard  cover,  which  will  prevent  fragments 
of  the  solid  from  flying  out  of  the  mortar.  Often,  it  is  better  to  wrap 
the  solid  in  a  paper  or  cloth  and  then  to  break  it  with  blows  of  a 
hammer.  In  using  a  mortar  for  pulverizing,  it  is  better  to  put  only 
a  small  quantity  of  the  substance  into  the  mortar  at  once,  sifting  it 
frequently  and  returning  the  coarser  particles  to  the  mortar  for 
further  trituration.  The  sifting  may  be  done  by  rubbing  the  powder 
lightly  with  the  finger  upon  a  piece  of  muslin  tightly  stretched  over 
the  mouth  of  a  beaker  (Fig.  144). 

12.  The  Pneumatic  Trough. — For  collecting  gases  over 
water,  the  pneumatic  trough,  in  some  form,  is  indispensable.  A  con- 
venient trough  is  shown  in  Fig.  6  and  described  in  £  20.  The  pan,  /, 
may  be  of  earthenware,  while  a  flower  pot  saucer  will  answer  for  e. 
Two  flat  blocks  of  any  material  heavier  than  water  may  be  used,  in- 
stead of  the  saucer,  for  the  support  of  the  inverted  gas  receiver,  g. 
With  this  apparatus,  the  receiver  must  be  filled  outside  of  the  trough. 
The  mouth  being  closed  with  the  hand,  a  flat  piece  of  wood,  glass 


APPENDIX.  329 

or  card  board,  the  bottle  may  be  quickly  inverted  and  placed  in  posi- 
tion so  that  its  mouth  is  closed  by  the  water  in/.  If  any  air  gets 
into  g  during  this  operation,  the  work  must  be  done  again.  While 
one  bottle  is  filling  with  gas,  another  is  to  be  made  ready.  When 
filled  with  gas,  the  first  bottle  may  be  removed  from  the  trough  by 
slipping  a  shallow  plate  or  saucer  beneath  its  mouth  and  removing 
plate  and  bottle  together.  Enough  water  will  be  retained  in  the 
plate  to  seal  the  mouth  of  the  bottle.  If  the  lip  of  the  bottle  has 
been  ground  flat,  as  recommended  in  App.  4,  h,  a  piece  of  window 
glass  will  answer  instead  of  the  plate.  As  successive  bottles  are 
filled,  the  trough  may  become  inconveniently  full  of  water  some  of 
which  may  be  dipped  out  or  removed  with  a  rubber  tube  siphon 
(Ph.,  §298). 

Any  bucket  or  tub  with  a  hanging  shelf  having  holes  bored  in  it, 
will  make  an  efficient  pneumatic  trough. 

When  it  can  be  secured,  a  pneumatic  trough  similar  to  that  shown 
in  Fig.  145,  is  desirable.  It 
may  be  made  of  boards  care- 
fully joined  and  painted,  but  is 
preferably  lined  with  sheet 
lead.  It  should  be  sunk  in  a 
table  and  provided  with  a  wa- 
ter cock  and  drain  pipe.  Gas 
receivers  are  easily  filled  with 
water  in  the  well,  mn,  and 
placed  upon  the  shelf,  b,  which 
is  to  be  below  the  water  level. 

The  dimensions  of  mn  are  to  be  determined  by  the  size  of  the  largest 
vessels  that  are  to  be  sunk  in  it  and  the  size  of  b  by  the  size  and 
number  of  gas  receivers  that  are  likely  tcr  be  in  use  at  any  one  time. 
Grooves  may  be  provided  in  the  shelf,  b,  running  parallel  to  the  side, 
ac.  These  grooves  allow  the  rubber  delivery  tube  to  pass  under  the 
edge  of  the  receivers  without  compression.  In  lifting  large  receivers 
from  the  well  of  a  small  trough,  the  water  level  may  be  brought 
below  the  shelf,  b.  Under  such  circumstances,  more  water  may  be 
introduced  from  a  pail  or  by  the  water-cock,  or  a  jug  of  water  pre- 
viously placed  within  convenient  reach,  may  be  placed  in  the  well 
and  subsequently  removed  when  the  filling  cf  the  receiver  with  gas 
raises  the  level  of  the  water  too  high. 

Porcelain  pneumatic  troughs  for  use  with  mercury  (Exp.  6)  may  be 
bought  for  a  little  money,  of  any  dealer  in  chemical  wares,  but  one 
may  be  made  of  a  block  of  hard  wood.  Its  principal  dimension 
should  be  horizontal,  the  bottom  being  rounded  so  that  it  will  con- 


330  APPENDIX. 

form  to  the  outline  of  a  test  tube  or  cylinder  placed  in  it.  Its  depth 
should  be  a  little  more  than  the  diameter  of  the  test  tube  or  cylinder 
used. 

In  collecting  gases  over  water,  two  difficulties  must  be  guarded 
against.  First,  if  from  any  cause,  the  tension  of  the  gas  within  the 
apparatus  becomes  less  than  the  atmospheric  pressure,  water  from 
the  pneumatic  trough  may  be  forced  back  through  the  delivery  tube 
into  the  generating  flask.  Cold  water  being  thus  suddenly  admitted 
to  a  hot  flask,  the  latter  is  broken  and  sometimes  a  more  serious  ex- 
plosion takes  place.  This  danger  is  especially  present  in  thus  col- 
lecting a  gas  somewhat  soluble  in  water.  See  Exp.  65  and  §  79.  In 
stopping  the  evolution  of  a  gas,  remove  the  delivery  tube  from  the 
trough,  and  remove  the  adhering  water  drops  before  removing  the 
lamp.  Whenever  the  delivery  of  a  gas  begins  to  slacken,  watch  the 
delivery  tube ;  if  water  begins  to/  "  suck  back  "  toward  the  flask, 
quickly  remove  the  delivery  tube  from  the  water,  or,  still  better, 
break  the  caoutchouc  connection  recommended  in  App.  4,  b  (as  shown 
at  c,  Fig.  6.)  or  loosen  the  stopper  of  the  generating  flask.  When  a 
liquid  is  used  in  the  flask,  this  danger  of  "  sucking  back  "  may  be 
avoided  by  the  use  of  a  safety  tube,  as  shown  at  s,  Fig.  34.  In  case 
a  partial  vacuum  should  be  formed  in  the  flask,  b,  atmospheric  pres- 
sure would  force  down  the  liquid  in  the  lower  part  of  the  tube,  s, 
and  thus  admit  air  instead  of  raising  the  liquid  in  c,  to  the  greater 
height  necessary  to  allow  it  to  enter  b.  The  funnel  tubes  shown  in 
Figs.  32  and  62  act,  similarly,  as  safety  tubes. 

The  second  difficulty  to  be  guarded  against  is  the  production  of 
too  great  a  pressure  within  the  apparatus  by  allowing  any  part  of 
the  delivery  tube  to  dip  too  far  beneath  the  surface  of  the  water  in 
the  trough.  Owing  to  the  high  specific  gravity  of  the  liquid  used, 
this  difficulty  is  especially  present  in  the  collection  of  gases  over 
mercury.  The  pressure  thus  produced  may  develop  leaks  in  the  ap- 
paratus or,  in  certain  cases  (Fig.  32),  force  the  liquid  of  a  flask  out 
through  the  funnel  or  safety  tube. 

13.  Gas  Holders. — It  is  often  convenient  to  have  a  supply  of 
oxygen,  hydrogen  and  other  gases  on  hand.  Gas  holders  (often  im- 
properly called  gasometers)  are  convenient  fo:*  storing  such  gases  for 
use.  One  form  of  easy  construction  is  shown  in  Fig.  146.  It  con 
sists  of  an  outer  vessel,  a,  open  at  the  top,  and  an  inner  vessel,  b, 
open  at  the  bottom.  Both  may  well  be  made  of  galvanized  iron  ;  a 
may  be  a  barrel,  cask  or  earthen  crock.  The  upper  end  of  b  is  ham- 
mered into  saucer  shape  so  that  its  highest  point  shall  be  at  the 
middle.  At  this  highest  point  is  inserted  a  gas  cock,  having  its  free 


A  PPENDIX. 


331 


end  smooth  and  slightly  tapering,  for  the  reception  of  rubber  tub- 
ing. Three  hooks  or  eyes  are  attached  to  the 
edge  of  the  upper  end  of  b,  from  which  extend 
cords  that  are  knotted  together  at  the  lower  end 
of  the  supporting  cord,  c.  The  cord,  c,  may  pass 
over  pulleys  in  a  frame,  as  shown  in  the  figure, 
or  over  pulleys  supported  from  the  ceiling,  the 
frame  being  omitted.  Fill  a  with  water.  Open 
the  stop  cock,  remove  the  weights  from  c  and 
allow  b  to  sink  into  a.  Be  sure  that  there  is 
enough  water  in  a  to  cover  the  highest  point  of  b. 
Connect  the  stop  cock,  by  rubber  tubing,  with 
the  gas  generator,  but  not  until  all  air  has  been 
expelled  from  the  tubing.  Open  the  stop  cock 
and  place  weights  at  the  free  end  of  c.  By  mak- 
ing these  weights  heavier  than  b  the  pressure  in 
the  generating  apparatus  may  be  reduced  as  far 
as  desired.  As  gas  is  delivered,  b  will  rise.  The 
apparatus  is  shown  on  a  larger  scale  at  (r,Fig.  93. 
When  the  generation  of  gas  has  ceased,  or  when  b  is  full,  close  the 
stop  cock,  remove  the  tubing  and  leave  suspended  from  c  only 
enough  weights  to  counterbalance  b.  For  most  schools,  a  6  or  8 
gallon  crock  (preferably  tall  and  narrow)  will  be  large  enough  for 
the  outer  vessel.  The  stop  cock  may  be  had  of  any  plumber  or  gas 
fitter  ;  any  tinsmith  can  make  the  vessel,  b, 

When  gas  is  wanted  from  the  holder,  as  in  Exp.  49,  connect  the 
gas  cock  of  b  with  the  apparatus  to  be  used,  open  the  cock,  remove 
weights  from  c  and,  if  necessary  to  produce  the  desired  pressure, 
place  them  upon  b.  It  is  customary  to  paint  the  oxygen  holder  red 
and  the  hydrogen  holder  black,  for  purposes  of  ready  distinction. 

A  convenient  form  of  gas  holder,  which  may  be  made  of  metal 
and  of  any  desired  size  is  shown  in  Fig.*147.  The  open  cistern ,  s,  which 
is  better  made  cylindrical,  is  connected  with  the  closed  cistern,  g,  by 
two  tubes  provided  with  stop  cocks.  One  of  these,  t,  passes  nearly 
to  the  bottom  of  g,  while  the  other  just  enters  the  top  of  g  without 
projecting  into  it.  A  third  tube,  also  provided  with  a  stop  cock, 
passes  from  the  top  of  g  and  carries  a  piece  of  rubber  tubing.  The 
oblique  tube,  i,  at  the  bottom  of  g,  may  be  closed  with  a  cork  or 
screw  plug.  The  apparatus  may  be  placed  over  a  tub  or  in  a  shal- 
low pan  provided  with  a  drain  pipe.  To  fill  this  holder,  close  {,  open 
all  three  stop  cocks  and  pour  water  into  s.  As  water  enters  g,  air 
escapes  through  the  rubber  tube.  When  g  is  filled  with  water, 
close  the  stop  cocks,  remove  the  plug  from  i  and  insert  the  delivery 


332 


APPENDIX. 


tube  of  the  gas  generator.  As  gas  enters  g,  water  escapes  at  i. 
When  g  is  filled  with  gas,  remove  the  tube 
from  i  and  insert  the  plug.  When  desired, 
s  may  be  used  as  a  pneumatic  trough  by 
partly  filling  it  with  water,  inverting  a  re- 
ceiver filled  with  water  over  the  upper  end 
of  n,  and  opening  the  stop-cocks  of  n  and  t. 
Water  enters  g  by  t  and  gas  rises  through  n 
into  s  and  the  inverted  receiver.  When 
desired,  the  cock  of  n  may  be  left  closed 
and  the  other  two  opened.  Water  from  s 
will  then  force  gas  out  through  the  rubber 
tube. 

A  convenient  gas  holder  may  be  made 
from  a  large  glass  bottle  or  a  jug  by  pass- 
ing two  glass  tubes  through  the  cork,  pro 
viding  one  with  a  piece  of  rubber  tubing 
and  the  other  with  a  stop  or  pinch  cock 
(App.  20)  all  as  shown  in  Fig.  148.  The  lot- 
tie  being  filled  with  water,  the  gas  genera- 
FIG.  147.  tor  is  connected  with  the  stop-cock  which  is 

then  quickly  opened.    As  the  gas 

enters  g  through  a,  water  es- 
capes through    the    siphon,    c. 

The  pressure  on  the  generator 

at  starting,  may  be  relieved  by 

sucking  at  c  to  start  the  action 

of  the  siphon.     Gas  is  delivered 

from  g  through  a,  by  connecting 

c  with  a  supply  of  water  elevated 

on  a  shelf  (siphon  delivery,  jf 

desired)  or  with  any  other  sup- 
ply of    water  under   moderate 

pressure.     Any    one    of    these  FIG.  148. 

three  forms  of  gas  holders,  when  filled  with  water,  may  be  used  as 

an  aspirator  (Exp.  57). 

When  a  gas  is  to  be  kept  for  only  a  short  time,  a  caoutchouc  gas 

bag  is  a  convenient  substitute  for  a  gas  holder.     It  is  easily  portable 

and  has  other  advantages.     One  may  be  bought  for  two  or  three 

dollars. 
14.  Drying    Oa§e§.  —  Several    ways   of  freeing  gases  from 

aqueous  vapor  are  illustrated  in  Exps.  28,  31,  57,  61  and  88.    When 

sulphuric  acid  is  used,  the  method  given  in  Exp.  31  is  preferable  to 


APPENDIX.  333 

that  given  in  Exp.  88.  See  Figs.  45  and  64.  Drying  tubes  of  vari- 
ous other  forms  may  be  had  of  dealers  in  chemical  glassware.  In 
using  a  drying  tube,  care  should  be  taken  that  there  are  no  straight 
passages  through  which  the  gas  can  find  quick  and  easy  passage.  A 
loose  plug  of  cotton  wool  is  generally  placed  at  each  end  of  the  dry 
ing  tube  to  keep  the  solid  drying  agent  in  place.  If  quicklime  be 
used,  allowance  must  be  made  for  its  expansion  when  acted  upon  by 
moisture.  The  choice  of  drying  agent  must  often  be  determined  by 
the  chemical  relations  of  the  gas  to  be  dried.  Thus,  sulphuric  acid 
or  calcium  chloride  could  not  be  successfully  employed  in  Exp.  61, 
nor  quicklime  in  Exp.  148.  Phosphoric  anhydride  is  sometimes  used 
for  drying  gases. 

15.  l<ainp§. — In  laboratories,  where  illuminating  gas  is  pro- 
vidtd,  the  most  convenient  form  of  lamp  for  heating  purposes  is  the 
Bunsen  burner,  represented  in  Figs.  16, 18,  etc.  It  gives  a  very  hot 
and  smokeless  flame.  A  fair  substitute  for  a  Bunsen  burner  may  be 
made  by  inverting  a  wide  necked 
glass  funnel  over  any  ordinary  gas 
burner,  supporting  it  in  any  con- 
venient way  so  that  air  may  have 
free  passage  between  the  sides  of 
the  burner  and  the  glass  as  shown 
in  Fig.  149.  The  funnel  is  to  be  put 
into  position  before  the  gas  is 
lighted.  The  gas  supply  is  to  be  fj 
controlled  so  as  to  produce  a  smoke- 
less flame. 
When  a  very  small  flame  is  used 

with  the  Bunsen  burner,  the  flame  may  drop  down  into 
the  tube.  This  may  be  prevented  by  laying  a  small 
piece  of  wire  gauze  over  the  top  of  the  tube  and  press- 
ing its  edges  down  against  the  sides  of  the  tube,  before 
lighting  the  gas.  A  long  flame  for  heating  tubing 
may  be  secured  by  slipping  the  attachment  represented 
in  Fig.  150  over  the  tube  of  the  Buusen  burner. 

A  Bunsen  burner  may  be  obtained  of  any  dealer  in 
chemical  supplies.     Write  for  a  catalogue  of  chemical 
FIG.  150.      apparatus  to  Bullock  and  Crenshaw,  Philadelphia. 
When  gas  is  not  provided,  the  alcohol  lamp,  represented  in  Figs. 
3,  60,  etc.,  is  generally  used.     Under  similar  circumstances,  the  Vapor 
Bunsen  Burner,  represented  in  Fig.  151,  will  be  found  very  efficient. 
It  is  provided  with  additional  burners  for  evaporating  and  blowpipe 
urposes,  burns  gasoline,  and  serves  as  a  retort  stand,     Gasoline  is 


334 


APPENDIX. 


much  cheaper  than  alcohol. 
S.  Kellogg,  Cleveland,  O. 


The  lamp  may  be  obtained  of  James 

The  Berzslius  or  argand  lamp  burns 
alcohol,  and  is 
convenient  for 
many  purposes 
\vbere  much 
heat  is  neces- 
sary, e.  g.,  the 
preparation  of  Gl 
oxygen  in  con- 
siderable quan- 
tity. It  may  be 
had  of  Queen 
&  (^..Philadel- 
phia, or  any  other  dealer  in  apparatus. 


FIG.  153. 
FIG.  151. 

16.  Fletcher  Burners. — Special  heating  apparatus  is  now 


FIG.  154. 


FIG.  155. 


made  in  great  variety.  Of  the  many  forms  offered  to  the  public, 
none  seem  more  desirable  than  those  designed  by  Thomas  Fletcher 
of  Warrington,  England,  and  supplied  in  this  country  by  the  Buf- 
falo (N.  Y.)  Dental  Manufacturing  Co.  This  paragraph  is  devoted  to 
this  apparatus.  The  "  Low  Temperature  Burner  "  is  shown  in  Fig. 
152.  It  gives  a  wide  range  of  temperature  and  dispenses  with  drying 


APPENDIX. 


335 


closets,  sand  and  water  baths.  It  burns  gas  and  is  furnished  with 
or  without  the  blast  pipe,  C.  (See  App.  17.)  Fig.  153  represents  the 
"  Evaporating  Burner,"  which  is  very  convenient  for  heating  flasks, 
as  in  >5  79,  a,  and  for  many  other  purposes.  By  the  addition  of  a  per- 
forated  cylinder  carrying  strong  wire  netting  to  the  ' '  Evaporating 
Burner,"  we  produce  a  "  Hot  Air  Bath,"  convenient  for  many  labora- 
tory purposes.  It  is  shown  in  Fig.  154.  The  ' '  Solid  Flame  Burner  " 
is  shown  at  one-fourth  actual  size  in  Fig.  155.  It  will  boil  2  I.  of 
water  in  six  or  seven  minutes,  and  may  be  used  for  melting  zinc  in 
an  iron  ladle,  as  directed  in  §  21. 

Other  pieces  of  the  "  Fletcher  "  apparatus  will  be  mentioned. 

17.  Blowers  and  Blowpipes.  —  For  working  tubes  of 
considerable  size,  a  blower  and  blast  lamp  are  necessary.  The  blower 


FIG.  156. 


FIG.  157. 


may  easily  be  made.    Fig.  156  shows  it  in  perspective,  and  Fig.  157 
in  section.    The  sides  of  the  bellows,  m,  and  of  the  reservoir,  n,  are 


FIG.  158. 


FIG.  159. 


made  of  leather  nailed  to  the  boards  at  top  and  bottom.     The  ar- 
rangement of  valves  is  evident  from  Fig.  157.    A  spring  keeps  a  con- 
.  stant  pressure  on  the  air  in  n.     Air  is  delivered  through  the  tube,  t, 
and  conducted  to  the  blast  lamp  by  flexible  tubing.     The  length,  ab, 


336 


APPENDIX. 


may  be  about  60  cm.    A  more  desirable  form,  made  by  the  Buffalo 

(N.  Y.)  Dental  Manufacturing  Co.,  is 
shown  in  Fig.  158.  A  Bunsen  blast 
lamp  is  shown  in  Fig.  159.  Gas  enters 
by  the  tube  at  the  right.  The  other 
tube  is  connected  with  the  blower.  It 
may  be  had  of  James  W.  Queen  &  Co., 
Philadelphia.  The  temperature  may 
be  increased  by  placing  the  glass  to  be 
heated  before  a  piece  of  charcoal  upon 
which  the  flame  plays.  Fig.  160  shows 
a  "  Hot  Blast  Blowpipe  "  furnished  by 
the  Buffalo  Dental  Manufacturing  Co. 
The  upright  jet  may  be  used  for  light 
or  for  a  moderate  heat  for  bending  tub- 
ing, etc.  It  is  arranged  so  that  it  may 
be  bent  down  to  ignite  the  blowpipe 
jet  at  c,  as  shown  by  the  dotted  lines. 
The  air  pipe  is  coiled  around  the  gas 
pipe  and  both  are  heated  by  a  small 
Bunsen  burner  beneath.  This  blow- 
pipe gives  a  pointed  flame  that  will  melt  a  fine  platinum  wire. 

When  gas  can  not  be  had,  alcohol,  naphtha  or  oil  may  be  used  with 
the     mouth     or    blast    ..... ^. 

\ 


WICK  HOLDER  TURNED 
HALF  A.  REVOLUTION*   .;' 


blowpipe  for  many  pur- 
poses. A  large  wick  is 
essential  which,  with  its 
holder,  should  be  cut 
obliquely,  so  that  the 
flame  may  be  directed 
downward  when  neces- 
sary. The  lamp  should 
be  of  such  a  form  that  the 
work  may  be  held  close 
to  the  wick.  A  desir- 
able lamp  for  such  pur- 
poses, furnished  by  the 
Buffalo  Dental  Manu- 
facturing Co.,  is  shown 
in  Fig.  161,  The  wick  holder  may  be  adjusted  at  any  angle  desired 
by  turning  it  in  its  collar.  The  cut  is  half  the  size  of  the  actual 
lamp.  Any  such  lamp  may  be  used  with  a  common  mouth  blowpipe, 


FIG.  161. 


APPENDIX.  337 

such  as  is  shown  in  Fig.  162,  or  with  the  blast  from  the  blower.  An 
attachment,  similar  to  that  shown  in  Fig.  150,  may  be  added  to  the 
Bunsen  burner  for  blowpipe 
purposes.  A  blowpipe,  suf- 
ficient for  many  purposes, 
may  be  made  from  glass  tub-  •FlG-  l62- 

ing.  Blowpipes  may  ba  bought  in  a  great  variety  of  forms.  In  using 
the  mouth  blowpipe,  air  should  be  forced  through  it  by  the  action  of 
the  cheeks  rather  than  by  the  action  of  the  lungs.  A  little  practice 
will  enable  teacher  or  pupil  thus  to  maintain  a  continuous  current  of 
air  from  the  nozzle,  breathing  naturally  in  the  meantime.  See  the 
Tinner's  Soldering  Lamp,  App.  18. 

18.  Soldering.— The  teacher  or  pupil  will  often  find  it  very 
convenient  to  be  able  to  solder  together  two  pieces  of  metal.  A  bit 
of  soft  solder,  the  size  of  a  hazlenut,  may  be  had  gratis  of  any  good 
natured  tinsmith  or  plumber.  Cut  this  into  bits  the  size  of  a  grain 
of  wheat.  Dissolve  a  teaspoonful  of  zinc  chloride  in  water  and  bot- 
tle it.  It  may  be  labelled  "  soldering  fluid."  Having  bought  or 
made  an  alcohol  lamp  (Ph.,  App.  B),  you  are  ready  for  work.  For 
example,  suppose  you  are  to  solder  a  bit  of  wire  to  a  piece  of  tinned 
ware.  If  the  ivire  be  rusty,  scrape  or  file  it  clean  at  the  place  of 
joining.  By  pincers  or  in  any  convenient  way  hold  the  wire  and  tin 
together.  Put  a  few  drops  of  "  soldering  fluid  "  on  the  joint,  hold 
the  tin  in  the  flame  so  that  the  wire  shall  be  on  the  upper  side,  place 
a  bit  of  solder  on  the  joint  and  hold  in  position  until  the  solder 
melts.  Remove  from  the  flame  holding  the  tin  and  wire  together 
until  the  solder  has  cooled.  The  work  is  done.  The  mouth  or  blast 
blowpipe,  previously  mentioned,  will  be  a  convenient  substitute,  in 
many  cases,  for  the  alcohol  lamp.  Where  gas  can  not  be  had,  the  "  tin- 
ner's soldering  lamp  "  is  convenient.  It  may  also  be  used  in  working 
glass.  At  the  base  of  a  perforated  sheet  iron  cylinder,  M,  is  a  metal  alco- 
hol lamp.  The  cylinder  supports  a  strong  metal  cup,  C,  beaten  into 
shape.  The  opening  by  which  the  alcohol  is  introduced  into  this  cup 
may  be  closed  by  a  cork,  which  will  then  act  as  a  safety  valve.  A  bent 
tube  passes  from  the  upper  part  of  the  cup  and  terminates  in  a  nozzle  of 
1  mm.  aperture,  midway  between  the  wick  of  the  lamp,  a,  and  the  bot- 
tom of  the  cup,  C,  The  flame  of  a  vaporizes  part  of  the  alcohol  in  C. 
This  vapor  escapes  under  pressure  at  the  nozzle,  where  it  ignites, 
forming  a  pointed,  horizontal  and  very  hot  flame,  which  protrudes 
through  the  opening  in  front.  The  bent  tube  may  pass  through  a 
slit  in  the  back  side  of  the  cylinder.  If  you  have  a  "soldering 


338  APPENDIX. 


FIG.  163. 

iron,"  you  can  do  a  wider  range  of  work,  as  many  pieces  of  work 
cannot  be  held  in  the  lamp  flame.  Fig.  163  shows  a  convenient  form 
of  heater  for  such  soldering  irons.  It  burns  gas. 

19.  Deflagration  Spoon.— A  deflagrating  spoon  for  burning 
phosphorus,  sulphur,  etc.,  in  oxygen  may  be  bought  for  a  few  cents 
of  any  apparatus  dealer.     One  may  be  made  by  soldering  the  bowl  of 
any  ordinary  metal  spoon  or  any  other  metal  cup  to  a  long  wire 
handle  and  bending  the  wire  upward  at  a  right  angle  near  the  cup. 
A  cup  may  be  hollowed  in  the  side  of  a  piece  of  chalk  or  lime  and 
then  fastened  to  a  wire  handle.     If  a  metal  cup  be  used  for  combus- 
tions in  oxygen,  it  is  well  to  line  it  with  some  infusible  materinllike 
clay,  powdered  chalk,  lime  or  plaster  of  Paris. .  A  coated  cork  cap- 
sule, smaller  than  the  one  mentioned  in  Exp.  58,  may  be  provided 
with  a  wire  handle  and  used  as  a  deflagrating  spoon.     In  any  case, 
the  upper  part  of  the  wire  handle  should  be  straight  so  that  it  may 
be  thrust  through  the  cover  of  the  jar. 

20.  Cocks. — Whenever  flexible  tubing  is  used,  pinch  cocks 

furnish  cheap  substitutes  for  stop 
cocks.  Fig.  164  shows  one  form ; 
other  forms  may  be  found  represented 
in  catalogues  of  dealers  in  chemical 
wares.  When  the  gas  is  to  flow,  the 
pinch  cock  is  placed  so  that  the  tub- 
FlG.  164.  ing  passes  through  the  open  space,  o  ; 

when  the  supply  is  to  be  cut  off,  the  tubing  is  compressed  between 
the  arms  at  c. 

A  s^op  cock  may  be  made  as  follows :  Provide  two  glass  tubes,  one 
of  which  slides  easily  into  the  other.  Close  one  end  of  the  smaller 
tubs  (App.  4,  d,)  and  with  a  rat-tail  file  wet  with  a  solution  of  cam- 
phor in  turpentine,  make  a  hole  in  the  side  2  or  3  cm.  from  the  closed 


APPENDIX. 


339 


end.     Connect  the  tubes  by  a  piece  of  rubber  tubing  that  snugly  fits 

the  smaller  tube.     When  the  smaller  tube  is  pushed  into  the  larger 

one  until  the  hole  in  the  side  is  visible  (Fig.  165)  the  cock  is  open  ; 

when  the  smaller  tube 

is    drawn   back    (Fig. 

166),  the  hole  is  closed 

by  the  rubber  tubing  FIG.  165. 

and  the  cock  is  closed.  A  very  simple  valve  for  controlling  the  flow 

I  of  fluids  may  be  made 
by  placing  a  glass  ball 
in  a  piece  of  soft  rubber 
tubing.  The  ball  should 

be  larger  than  the  opening  in  the  tubing.     By  pinching  the  rubber 

at  the  side  of  the  ball,  a  little  channel  is  made  through  which  the 

liquid  or  gas  may  pass. 


FIG.  166. 


21.    Evaporating    Dishes,    Crucibles    and    Fur- 
naces.— Evaporating  dishes  may  be  had  made  of  porcelain  and  pro- 


FIG.  167. 


FIG.  168. 


vided  with  a  projecting  lip  and  glazed  on  both  sides  or  only  en  the 
inside.  The  latter  are  the  cheaper  but  the 
former  are  the  more  desirable.  Sizes  from 
8  to  15  cm,  in  diameter  are  best  adapted  to 
the  needs  of  most  classes.  They  should  be 
supported  upon  wire  gauze,  the  sand  or 
water  bath  and  never  exposed  to  the  naked 
flame.  For  granulating  zinc  (§  21)  or  fusing 
salt  (§  99),  Hessian  crucibles  are  cheap  and 
largely  used.  They  will  endure  a  very 
high  temperature  but  should  be  heated 
somewhat  gradually.  They  may  be  heated 
in  a  coal  or  coke  fire  in  any  ordinary  stove. 
Heated  crucibles  may  be  handled  conven- 
FIG.  160.  iently  with  crucible  tongs,  two  common 


340 


APPENDIX. 


forms  of  which  are  represented  in  Fig.  168.  They  may  be  had  of 
Bullock  &  Crenshaw,  Philadelphia.  Small  clay  crucibles  and  cap- 
sules are  very  valuable  pieces  of  apparatus.  With  the  Fletcher 
"  Blowpipe  Furnace  "  and  the  clay  crucible  shown  in  Fig.  169,  several 
grams  of  cast  iron  may  be  melted  in  a  very  few  minutes.  For  melting 
iron,  brass,  copper,  etc.,  up  to  quantities  of  five  or  six  pounds,  the 
"  Injector  Gas  Furnace,"  shown  in  Fig.  170,  and  a  plumbago  crucible, 


AIR  CHECK 


FIG.  170. 

are  convenient  and  efficient.  The  plumbago  crucible  must  be  heated 
slowly  the  first  time  it  is  used.  Smaller  quantities  (about  1  Kg.\  of 
such  metals  may  be  melted  in  a  plumbago  crucible,  by  the  Fletcher 


FIG.  171. 

"  Crucible  Furnace  for  Petroleum,"  shown  in  Fig.  171.  These  three 
Fletcher  Furnaces  require  the  aid  of  the  "  Blower,"  shown  in  Fig. 
156  or  158. 

2*2.   Uletal  Retorts.— Oxygen  maybe  prepared  by  carefully 
heating  the  materials  in  a  Florence  flask  or  glass  retort,  but  for  this 


APPENDIX.  341 

and  other  processes,  where  high  temperatures  are  used,  as  in  the  prepa- 
ration of  illuminating  and  marsh  gases,  an  iron  or  copper  retort  is 
very  desirable.  Such  retorts  may  be  had  in  a  variety  of  forms,  made 
of  iron,  sheet  iron  or  copper,  of  dealers  in  chemical  or  philosophical 
apparatus,  at  prices  ranging  from  $1  upwards.  The  author  has  made 
a  very  cheap  and  wholly  efficient  retort  as  follows  :  Cut  a  thread  on 
each  end  of  a  piece  of  inch  or  f-inch  gas  pipe,  a,  6  or  8  inches  long/ 
Screw  an  iron  cap,  k,  over  one  end. 
For  the  other  end,  provide  an  iron  «! 
"reducer,"  t,  carrying  a  piece  of 
f-inch  gas  pipe,  e,  about  15  or  18  FIG.  172. 

inches  long.  The  materials  being  placed  in  the  capped  tube,  the  re- 
ducer with  its  pipe  is  screwed  on  the  open  end  of  the  tube.  The 
closed  retort  may  then  be  thrust  into  the  coals  of  any  ordinarystove. 
A  piece  of  glass  tubing  maybe  sealed,  with  plaster  of  Paris,  into  the 
end  of  the  small  iron  tube.  This  affords  a  good  means  for  connect- 
ing the  retort  with  rubber  tubing  and  protects  the  latter  from  burn- 
ing.  If  desirable,  the  inner  surface  of  k  may  be  smeared  with  wet 
plaster  of  Paris  before  screwing  it  upon  a.  If,  at  the  end  of  the  ex- 
periment, t  is  not  easily  removed  from  a,  a  few  blows  will  generally 
start  it.  The  parts  of  this  retort  may  be  had  of  any  gas  or  steam 
fitter. 

A  sheet  iron  retort  may  be  made  by  any  tinner  as 
follows :  the  conical  piece,  ia,  has  a  horizontal  flange 
turned  around  its  lower  edge  at  a.  The  circular 
bottom  piece  has  its  edge  turned  over  this  flange, 
as  shown  in  the  sectional  figure,  and  hammered 
down.  The  joint  on  the  sloping  side,  ia,  is  lapped 
and  hammered,  as  is  generally  done  in  making 
,  stove  pipe.  The  mouth  at  i  is  made  slightly  flaring 
FIG.  173.  by  hammering,  to  admit  a  cork  carrying  a  glass  de- 
livery tube.  The  joints  may  be  sealed  by  washing  them  on  the  inside 
with  a  thin  paste  of  plaster  of  Paiis.  The  cork  may  be  protected 
from  over  heating  by  providing  a  cup,  cc,  which  may  be  filled  with 
water  or  a  wet  cloth. 

A  good  retort  may  be  made  by  luting  on  the  cover  of  a  small  iron 
kettle  and  connecting  a  delivery  tube  with  its  nose. 

23.  Ventilating  Chamber,  etc. — A  chamber,  50  cm.  by 
75  cm.  or  larger,  with  glass  sides  and  provided  with  a  ventilating  flue 
that  has  a  good  draft,  is  important  for  experiments  with  chlorine, 
hydrogen  sulphide,  etc.  The  ventilating  flue  may,  in  some  cases, 
be  advantageously  connected  with  the  chimney.  It  may  be  built 
against  the  chimney  and  provided  with  two  or  three  narrow  slits 


342  APPENDIX. 

through  the  brick  work  from  top  to  bottom  of  the  closet.  At  least 
one  side  of  the  chamber  should  be  made  so  that  it  may  be  opened, 
but  when  shut,  it  should  fit  closely.  Openings  that  may  ba  closed, 
should  be  made  in  the  bottom  of  the  chamber  for  the  admission  of 
air  so  that  a  current  may  be  obtained.  A  lamp  burning  in  the  cham- 
ber will  aid  in  keeping  up  the  current  and  carrying  off  the  offensive 
gases. 

24.  Test  Papcr§,  etc.— Litmus  paper,  both  blue  and  red, 
should  be  kept  on  hand  for  the  detection  of  acids  and  alkalies.  Lit- 
mus is  a  blue  coloring  matter  prepared  from  certain  lichens  and  found 
in  commerce  in  small  cubical  masses  somewhat  soluble  in  water. 
White,  unsized  paper  is  stained  with  an  infusion  of  30  g.  of  litmus 
in  250  cu.  cm.  of  boiling  water.  Such  a  paper  is  reddened  by  an  acid 
(Exps.  41,  106,  etc.).  The  blue  litmus  paper  may  be  faintly  reddened 
by  immersion  in  vinegar  or  any  other  dilute  acid.  This  reddened 
paper  is  colored  blue  by  the  action  of  an  alkali  (Exp.  64). 

A  purple  liquid  may  be  prepared  by  steeping  red  cabbage  leaves 
in  water  and  filtering.  Such  a  cabbage  solution  will  be  colored  red 
by  an  acid,  or  green  by  an  alkali.^  Prepare  such, a  solution.  To  a 
part  of  it,  add  a  few  drops  of  sulphuric  acid  ;  it  will  become  red.  To 
another  part,  add  a  few  drops  of  a  solution  of  potassium  hydrate  ;  it 
will  become  green.  With  constant  stirring,  cautiously  pour  the  red 
liquid  into  the  green.  At  first,  the  red  color  will  disappear  and  the 
compound  appear  green,  but,  by  continued  addition  of  the  red  liquid, 
a  point  will  be  reached  when  the  compound  will  be  blue  instead  of 
green.  The  acid  and  alkali  are  then  mutually  neutralized.  Com- 
pare Exp.  78. 

A  ruby  red  tincture  of  cochineal  may  be  prepared  by  digesting  3#. 
of  cochineal  in  a  mixture  of  50  cu.  cm.  of  alcohol  and  200  cu.  cm.  of 
water  at  the  ordinary  temperature  for  several  days.  Acids  will 
change  the  color  of  such  a  tincture  to  orange  ;  alkalies  will  change 
it  to  violet  carmine. 

Turmeric  paper,  prepared  by  staining  unsized  paper  with  a  tincture 
(alcoholic  solution)  of  turmeric  root  (curcuma),  is  sometimes  used  as 
a  test  for  alkalies  which  turn  it  from  yellow  to  brown  (Exp  64). 
See  also  Exps.  99  and  100. 


FIGURES  REFER  TO  PARAGRAPHS,  UNLESS  OTHERWISE  SPECIFIED, 


Acetic  acid,  215. 
Acetyl,  2150:. 

"       hydrate,  215,  a. 
"       hydride,  215,  a. 
Acetylene,  219. 
Acid,  Acetic,  215. 

"  Anhydrosulphuric,  Ex.  6,  p.  136. 

"  Arsenic,  etc.,  249. 

"  Basicity  of  an,«i64. 

"  Binary,  163,  b. 

"  Boracic,  173. 

"  Boric,  173. 

"  Bromic,  etc.,  116. 

"  Carbonic,  198. 

"  Chamber,  152,  c. 

"  Chlorhydric,  104. 

"  Chloric,  etc'.,  112. 

u  Chromic,  381,  &. 

"  Cyanhydric,  205. 

"  Definition  of,  163. 

"  Disulphuric,  156. 

"  Fluorhydric,  122. 

"  Fuming  sulphuric,  156. 

"  Glacial  phosphoric,  242,  e. 

"  Haloid,  123,  b. 

"  Hydrochloric,  104. 

"  Hydrocyanic,  205. 

"  Hydrofluoric,  122. 

"  hydrogen,  166,  b. 

"  Hydrosulphuric,  137. 

"  Hyponitrous,  82. 

"  lodic,  etc.,  118. 

"  Manganic,  376,  e. 

'*  Metaphosphoric,  see  Phosphoric. 

u  Molybdic,  382. 

"  Muriatic,  104. 

41  Nitric,  73. 


Acid,  Nitro-hydrochloric,  114. 

"     Nitro-murialic,  114. 

"     Nitrous,  86. 

"     Nordhausen,  156. 

"     Oxalic,  Exp.  289. 

"     oxides,  165. 

"     Permanganic,  376,  f. 
Phosphoric,  etc.,  242. 

"     Prussic,  205. 

"  Pyroboric,  173,  b. 
Pyroligneous,  215. 
Pyrophosphoric,  242. 

"     salts,  170. 

"     Silicic,  Exp.  217. 

"     Stannic,  389. 

"     Sulphuric,  etc.,  149,  151,  157,  158. 

"     Ternaty,  163,  c. 

"     Thionic,  158. 

"     Tungstic,  383, 
Acidity  of  bases,  166,  b. 
Acids,  Nomenclature  of,  163. 
Affinity,  Chemical,  8,  9. 
Agate,  232, «. 
Air,  45-49. 

"    slaked  lime,  290,  c. 
Alabaster,  294. 
Albumen,  223. 
Alcohol,  210. 
Aldehyde,  215,  a. 
Alkali,  167,  b. 

"      The  volatile,  168. 
Allotropism,  39. 
Alloys,  322  ;  303,  a. 
Alum,  349. 
Alumina,  348. 

Aluminium,  see  Aluminum. 
Aluminum,  344. 

"          bronze,  347. 


344 


INDEX. 


Figures  refer  to  Paragraphs,  unless  otherwise  specified. 


Aluminum,  group,  352. 
"  oxide,  348. 

sulphate,  349. 
Amalgam,  338. 
Amethyst,  232,  a. 
Amide,  Ex.  17.  p.  314. 
Amine,  96,  a  ;  Ex.  16,  p.  314. 
Ammonia,  66,  168. 

type,  96. 
Ammonium,  168,  286. 

chloride,  287. 
nitrate,  288. 

Amorphous,  Note,  p.  113. 
Amp' re's  law,  61. 
Analysis  defined,  18. 
"       of  water,  14. 
"       Quantitative,  Note,  p.  296. 
Anhydride,  165. 
Anhydrite,  294. 

Anhydrosulphuric  acid,  Ex.  6,  p.  136. 
Animal  charcoal,  186. 
Anthracite,  181. 

Antimoniuretted  hydrogen,  253,0. 
Antimony,  251, 

44         chlorides,  253,^. 
44         glance,  251. 
44          hydride,  253,  a. 
"         oxides,  253,  b. 
44         sulphides,  253,  c. 
Antozone,  38,  a. 
Aqua  fortis,  73. 
"     regia,  114. 
Argentum,  etc.,  see  Silver. 
Arrow  root,  228. 
Arsenic,  243. 

acid,  249. 
44        hydride,  245. 
41        oxides,  247,  248. 
44       sulphides,  250. 

White,  247. 

Arsemuret,  Note,  p.  217. 
Arseniuretted  hydrogen,  253,  a. 
Arsine,  245. 
Aspirator,  App.  13. 
Atom  defined,  5. 
Atomic  attraction,  8,  9. 
41       symbols,  56,  93. 
44       volume,  175,  a  ;  240.  e. 
"       weight,  64. 
Atomicity,  65  ;  92,  d ;  174. 


Attraction,  Forms  of,  8. 
Auric,  see  Gold. 
Aurous,  see  Gold. 
Avogadro's  law,  61. 
Azurite,  319,  a. 


Barley  sugar,  226,  c. 
Barite,  131,  b. 
Barium,  297. 
Baryta,  297. 
Base  defined,  166. 
Bases,  Acidity  of,  166,  b. 
Basic  ammonia,  168. 

"     hydrogen,  164. 

44     oxides,  166,  a. 

44     salts,  170. 
Basicity  of  acids,  164. 
Bauxite, 
Beakers,  App.  7. 
Beet  sugar,  226,  b, 
Bell  metal,  322,  388. 
Benzol,  221,  c. 
Beryllium,  305. 
Bessemer  steel,  371. 
Bicarbonate  of  sodium,  269. 

41          of  potassium,  279. 
Bichromate  of  potassium,  381,  c. 
Binary  acids,  123,  b. 

44      compounds,  59. 
Bismuth,  254. 
Bisulphide  of  carbon,  201. 
Bisulphate  of  sodium,  267,  c. 
Bituminous  coal,  181. 
Bivalent,  92,  a. 
Black  ash,  268,  a. 
Black-band  iron  stone,  354,  a. 
Black  lead,  179. 

Black  oxide  of  manganese,  376,  d. 
Blast  furnace,  359. 
Bleaching  powder,  292,  b. 
Blende,  131,  a  ;  301. 
Blister  steel,  370. 
Bloom,  356. 
Blower,  App.  17. 
Blowpipes,  App.  17. 
Blowpipe,  The  compound,  41. 
Blue  vitriol,  324. 
Bohemian  glass,  234,  a. 
Bone-black,  186. 


INDEX. 


345 


Figures  refer  to  Paragraphs^  unless  otherwise  specified. 


Bone  phosphate,  295. 
Boracic  acid,  173. 
Borax,  172,  271. 
Boric  acid,  173. 
Boron,  172. 
Bottle  glass,  234,  c. 
Brass,  303,  a  \  322. 
Braunite,  375. 
Bread  making,  229. 
Brimstone,  132,  d. 
Britannia  metal,  388,  a. 
Bromine,  115. 
Bronze.  322,  347,  388. 
Brown  sugar,  226. 
Bulbs,  Blowing,  App.  4,  e. 
Bunsen  burner,  App.  15. 
Butter  of  antimony,  253,  d. 
"      of  tin,  389. 


Cadmium,  306. 
Caesium,  285. 
Cairngorm-stone,  232,  a. 
Calamine,  301. 
Calcareous  waters,  293. 
Calcic,  see  Calcium. 
Calcite,  289. , 
Calcium,  289. 

"        carbonate,  293. 

"        chloride,  291. 

"        chloro-hypochlorite,  292,  b. 

"        hydrate,  292, 

"        tiypochlorite,  292,  b. 

"         light,  Exp.  49  ;  290. 

"        oxides,  290. 

"        phosphate,  295. 

"        stearate,  294,  a. 

"        sulphate,  294. 
Calomel,  342. 
Calx,  Note,  p.  246. 
Cane  sugar,  226. 
Caoutchouc  stoppers,  App.  8«r 
Caramel,  226,  c. 
Carbon,  177. 

"       disulphide,  201. 

"       dioxide,  196. 

"       group,  p.  155. 

"       monoxide,  193. 

"       oxides,  192. 
Carbonic  acid,  198. 


Carbonic  anhydride,  196. 
Carbonyl,  194,  b. 
Carburet,  Note,  p.  164. 
Carnallite,  276. 
Carnelian,  232,  a. 
Casein,  223. 
Casserite,  385. 
Cast  iron,  358. 
Catalysis,  31. 
Caustic  lime,  292. 
"       lunar,  332. 
"       potash,  280. 
"       soda,  270. 
Celestine,  296.  * 

Cellulose,  230. 
Cementation  steel,  370. 
Centesimal  computations,  130. 
Ceric,  see  Cerium. 
Cerium,  353. 
Cerous,  see  Cerium. 
Chalcedony,  232,  a. 
Chalcocite,  131,  a  ;  319,  a. 
Chalcopyrite,  319,  a. 
Chalk,  289. 
Chamber  acid,  152,  c. 
Charcoal,  184-191. 
Chemical  action,  TI. 

"         affinity,  8. 

"         changes,  10. 

"         equations,  127. 
Chemism,  8. 
Chemistry  defined,  13. 
Chili  nitre  or  saltpeter,  271,  b. 
Chlorate  of  potash,  281. 

"       of  potassium,  281. 
Chlorohydric  acid,  104. 
Chloride  of  antimonj',  253,  d. 

u        of  ethylene,  Exp.  209. 

"        of  hydrogen,  104. 

"        of  lime,  292,  b. 

"       of  methyl,  209. 

"       of  nitrogen,  113.      - 
Chlorine,  98. 

"         acids,  112. 

"         Diatomic,  174. 

"         group,  123. 

"         oxides,  in. 
Chloroform,  209. 
Chrome  alum,  381,  d. 

"       iron  ore,  381. 


346 


INDEX. 


Figures  refer  to  Paragraphs,  unless  otherwise  specified. 


Chrome,  yellow,  316,  b  \  381,  c. 
Chromic  acid,  38:,  b 
Chromite,  381. 
Chromium,  381. 

"          steel,  381. 
Cinnabar,  334,  340. 
Clay,  233,  344. 

"     iron-stone,  354,  a. 
Coal,  181,  184,  186. 

"     gas,  221. 

"     tar,  221,  c, 
Cobalt,  378. 
Cocks,  App.  20. 
Coin,  328,  379;  396. 
Coke,  182. 

Collection  of  gases,  21 ;  Exps.  15, 185. 
Colloid,  Exp.  218. 
Colored  glass,  234,  h. 
Columbium,  260. 

Combining  weight  of  compounds,  63. 
"  "      of  elements,  64,  a. 

Combustion,  33. 
Combustible,  43. 
Composition  of  elementary  molecules, 

65- 

Computations,  128-130. 
Compound  blowpipe,  41. 

"          radicals,  97. 
Compounds,  6,  12. 
Concentrated  lye,  270. 
Constitutional  symbols,  95. 
Cooking  soda,  269. 
Copper,  319. 

"       acetate,  215,  c  ;  324. 

"       arsenite,  324. 

"        carbonate,  324. 

"        glance,  319,  a. 

"       nitrate,  324. 

"       oxides,  323. 
pyrites,  319,  a. 

"       Ruby,  323. 

"       snlphate,  324. 
Coral,  289. 
Corks,  App.  9. 
Corrosive  sublimate,  343. 
Corundum,  348. 
Cream  of  lime,  292. 
Crith  defined,  24. 
Crocus,  362,  b. 
Crown  glass,  234,  b. 


Crucibles,  App.  21. 

Crucible  steel,  373. 

Cryolite,  120,  349. 

Crystal,  234,  d. 

Crystals,  Classes  of,  Note,  p.  113. 

Crystallization,  268,  b. 

"  water  of,  268,  c. 

Crystalloid,  Exp.  218. 
Cupric,  see  Copper. 
Cuprite,  319,  a. 
Cuprous,  see  Copper. 
Cyanhydric  acid,  205. 
Cyanogen,  204. 

D 

Davy's  glow  lamp,  Exp.  304. 

Davyum,  App.  i. 

Decipium,  App.  i. 

Definite  proportions,  Law  of,  90. 

Deflagrating  spoon,  App.  19. 

Deliquescence,  280,  a. 

Dextrin,  228. 

Dextrose,  22% 

Dialyser,  Exp.  218. 

Dialysis,  Exp.  218. 

Diamond,  178. 

Di ,  see  bi . 

Dicarbonate,  see  Bicarbonate. 
Dichromate,  see  Bichromate. 
Didymium,  353. 
Dimorphous,  Note,  p.  113. 
Disulphate,  see  Bisulphate. 
Disulphide  of  carbon,  201. 
Double  salts,  170. 
Drummond  light,  Exp.  49,  290. 
Drying  gases,  Exps.  61,  88  ;  App.  14. 
Dutch  leaf,  Exp.  74. 

u      liquid,  Exp.  209. 
Dyad,  92,  a. 

E 

Efflorescence.  268,  c. 

Egg  shells,  293. 

Element  defined,  6. 

Elements,  Molecular  composition  05,65. 

"        Nomenclature  of,  58. 

u        Electro-negative,  166. 

"         Electro-positive,  163. 

"         Table  of,  App.  i . 
Emerald,  344,  381. 
Emery,  348. 


INDEX. 


347 


Figures  refer  to  Paragraphs^ 


Empirical  symbols,  94. 
Epsom  salt,  300. 
Equations,  Chemical,  127. 
Equivalence,  92,  d. 
Erbium,  353. 
Etched  glass.  234, /. 
Etching,  77,  Exps.  126-8. 
Ethene,  217. 
Ether,  213. 
Ethine,  219. 
Ethyl,  211. 

"      hydrate,  211. 

"      oxide,  213. 
Ethylene,  217. 

u        chloride,  Exp.  209. 
Eudiometer,  42. 
Evaporating  dishes,  App.  21. 


Factors,  126. 
Feldspar,  233,  344. 
Fermentation,  210,  Exp.  187. 
Ferric,  see  Iron. 
Ferrous,  see  Iron. 
Fibrin,  223. 
Filtering,  App.  8. 
Flasks,  App.  7. 
Flint,  232,  a. 

"     glass,  234,  d. 
Florence  flasks,  App.  7. 
Flowers  of  sulphur,  132,  d. 
Flue  dust,  317. 
Fluorhydric  acid,  122. 
Fluorine,  120. 
Fluor  spar,  120. 
Flux,  359. 

Formulas,  Molecular,  Note,  p.  54. 
Fruit  sugar,  227. 
Fulminating  silver,  329. 
Fuming  sulphuric  acid,  156. 
Funnels,  App.  8. 
Funnel  tubes,  App.  4,  e. 
Furnaces,  App.  16  and  21. 
Fusible  metals,  256. 


Galena,  131,  a  ;  308,  313. 
Galenite,  308,  313. 
Gallium,  351. 
Galvanized  iron,  303,  b. 


unless  otherwise  specified. 

Garnet,  344. 
Gas  carbon,  183. 
"    holders,  App.  13. 
u    Illuminating,  221. 
Gases,  Collection  of,  21,  Exps.  15,  185. 

"      Drying,  Exps.  61,  88  ;  App.  14. 
Gay-Lussac's  law,  176. 

tower,  152,  c. 
Gelatin,  224. 

German  silver,  303,  a  •  379. 
Glacial  phosphoric  acid,  242,  e. 
Glass,  234. 

"     stoppers,  App.  9. 

"     Ruby,  395,  a. 

u     tubing,  App.  4,  a. 

"     Uranium,  384. 

"     working,  App.  4. 
Glauber's  salt,  267,  b. 
Glucinum,  305. 
Glucose,  227. 

Glow  lamp,  Davy's,  Exp.  304. 
Glover  tower,  152,  c. 
Glue,  224. 
Gold,  393. 
Graduates,  App.  5. 
Grape  sugar,  227. 
Graphic  symbols,  95. 
Graphite,  179. 

Gravimetric  computations,  128. 
Green  vitriol,  367. 
Gray  antimony,  251. 

"     oxide  of  mercury,  339. 
Gun  cotton,  230,  b. 
Gypsum,  131,  £;  294. 

H 

Haematite,  354,  a. 
Halogen  group,  123. 
Haloids,  123,  b. 
Hard  coal,  181. 

"     soap,  270 ;  278,  b. 

"     water,  294. 
Hartshorn,  66. 
Hausmanite,  375 • 
Heavy  spar,  131,  b  \  297. 
Hematite,  354,  a. 
Hemioxide,  323,  329. 
Heptad,  92,  a. 
Hexad,  92,  a. 
Hexivalent,  92,  a. 


348 


INDEX. 


Figures  refer  to  Paragraphs^  unless  otherwise  specified. 


Homologous  series,  220. 
Horn  silver,  330. 
Hydrargillite, 
Hydrates,  167. 
Hydraulic  main,  221,  e. 
Hydrocarbons,  206. 
Hydrochloric  acid,  104. 

"  "     type,  96. 

Hydrocyanic  acid,  205. 
Hydrofluoric  acid,  122. 
Hydrogen,  15.  19. 

Acid,  166,  b. 

"         antimonide,  253,  a. 

"         arsenide,  245. 

"         Basic,  164. 

"         carbide,  207. 

H         chloride,  104. 

"         Collection  of,  22. 

"         Combustion  of,  40. 

"         Diatomic,  174. 

"         dicarbide,  217. 

"         dioxide,  44. 

"         oxides,  44. 

"         peroxide,  44. 

"         persulphide,  Note,  p.  122. 

a         phosphide,  240. 

"         pistol,  Note,  p.  40. 

"         potassium  carbonate,  279. 

*'         preparation  of,  21. 

"         properties  of,  24,  25. 

"         purification  of,  26. 

"         salts,  170,  c,  Note,  p.  144. 

"         silicide,  231,  d. 

"         sodium  carbonate,  269. 

"         sodium  sulphate,  267,  c. 

"         sulphate,  151. 

"         sulphide,  137. 

"         Tests  of,  28. 

"         tones,  Exp.  29. 
type,  96. 

"         Uses  of,  27. 
Hydrosulphites,  Ex.  4,  p.  305. 
Hydroxides,  167. 
Hydroxyl,  44. 
Hyponitrous  acid,  82. 
Hyposulphites,  157  ;  158,  b. 


Illuminating  gas,  221. 
Indigo,  Exps.  269  and  270. 


Indium,  330. 
Inorganic  substances,  7. 
International  measures,  A  pp.  a. 
Inulin,  228. 
Inverted  sugar,  227. 
Iodide  of  nitrogen,  119. 
Iodine,  117. 
Iridiutn,  402. 
Iron, 354. 

"    carbonate,  367,  a. 

"    Cast,  358. 

•*    chloride,  366. 

"    cyanide,  368. 

"    Galvanized,  303,  b. 

"    group,  380. 

"    hydrates,  363. 

"    Malleable,  374. 

"    nitrate,  367,  a. 

"    ores,  354,  a. 

"    oxides,  362. 

"    Pig,  358. 

;4    pyrites,  132,  c :  364. 

"    salts,  365. 

"    spathic,  354,  a. 

''    specular,  354,  a. 

"    sulphate,  367. 

"    sulphide,  364. 

u    Wrought,  360. 
Isinglass,  224. 
Isomerism,  216. 
Isomorphism,  Note,  p.  113. 


Jasper,  232,  a. 
Jeweller's  rouge,  362,  b. 

K 

Kieserite,  300. 
King  of  metals,  395,  a. 


Lactose,  226,  d. 

Lagoon,  173,  d. 

Lamp-black,  185. 

Lamps,  App.  15  and  16. 

Lanthanum,  353. 

Laughing  gas,  79. 

Law,  Ampere's  or  Avogadro's,  61. 

"     Gay-Lussac's,  176. 

"     of  definite  proportions,  90. 


INDEX. 


340 


Figures  refer  to  Paragraphs,  unless  otherwise  specified. 


Law  of  multiple  proportions,  9: 
Lead,  308. 

"     acetate,  215,  c  \  314. 

"     Black, 179. 

u     carbonate,  314. 

"     chloride,  314  ;  316,  b. 

"     chromate,  316  b. 

"     group,  318. 

"     iodide,  316,  b. 

i;     oxides,  312. 

"     pencils,  179. 

''     poisoning,  315. 

"      Red,  312. 

"     Sugar  of,  314. 

'•     sulphide,  313. 

"     Tests  for,  316. 

"     tree,  Exp.  271. 

"     White,  314. 
Leblanc,  268. 
Levulose,  227. 
Lichtenberg's  metal,  256. 
Liebig  condenser,  Exp.  202. 
Lignite,  181. 
Lime,  290. 

"     Air  slaked,  290,  c. 

"     Caustic,  192. 

M     Chloride  of,  292,  b. 

"     Cream  of,  292. 

u     light,  290. 

"     Milk  of,  292. 

"•     Slaked,  292. 

"     soap,  292,  a  ;  294,  a. 

"     stone,  289,  293. 

*'     water,  292. 
Limestone,  289,  293. 
Limonite,  354,  a. 
Litharge,  312. 
Lithium,  283. 
Litmus  paper,  App.  24. 
Loadstone,  362,  c. 
Lunar  caustic,  332. 
Lye,  270,  278. 

M 

Matter  defined,  i. 

u      Divisions  of,  2. 
Mass  defined,  3. 
Magnesia,  299. 

"         alba,  300. 
Magnesite,  300. 


Magnesium,  298. 

"  carbonate,  300. 

chloride,  300. 
group,  307. 
oxide,  299. 
sulphate,  300. 
Magnetite,  354,  a. 
Malachite,  319,  a ;  324. 
Malleable  iron,  374. 
Maltose,  226,  d. 
Manganese,  375. 

salts,  377. 
oxides,  376. 
Manganic  acid,  376,  e. 

"         anhydride,  376,  e. 
Manganite,  376,  c. 
Maple  sugar,  226,  b. 
Marble,  289. 
Marsh  gas,  207. 
"      type,  96. 
Marsh's  test,  246. 
Mercury,  334. 

"         bromides,  342,  b  ;  343,  c. 
chlorides,  342,  343. 

"         iodides,  342,  b  ;  343,  <r. 

"         nitrates,  342,  a  ;  343,  b. 

«'        oxides,  339. 

"        salts,  342,  343. 

"         sulphates,  342,  a  ;  343,  b. 

*'         sulphide,  340. 
Metaboric  acid,  173,  a. 
Metallic  oxides,  166,  a. 
Metalloids,  see  Non-metals. 
Metals,  261. 
Metamerism,  216. 
Meta-phosphoric  acid,  242 ;  242,  e. 
Metathesis,  18. 
Methane,  207. 
Methyl,  208. 

"        chloride,  209. 

"       hydride,  207. 
Metric  measures,  App.  2. 
Mica,  233,  344. 

Microcosmic  salt,  Ex.  6,  p.  278. 
Microcrith,  62. 
Milk  of  lime,  292. 
Milk  sugar,  226,  d. 
Minium,  312. 
Mineral  coal,  181. 
Mirrors,  338. 


350 


INDEX. 


figures  refer  to  Paragraphs,  unless  other-wise  specified. 


Mispickel,  243. 

Mixed  gases,  Note,  p.  39. 

Mixtures,  12. 

Molasses,  226. 

Molecular  composition,  65. 

"         formulas,  Note,  p.  54. 

"         symbols,  57,  94-96  ;  261,  c. 

"         volume,  175. 

"         weight,  63. 
Molecule  defined,  4. 
"        Size  of,  4,  a 
Molybdenum,  382. 
Monad,  92,  a. 
Mortar,  292,  a  •  App.  n. 
Multiple  proportions,  Law  of,  91. 
Muriatic  acid,  104. 
Muscovado  sugar,  226. 

Bf 

Nascent  state,  114,  b. 

Natural  groups,  123,  162,  257,  318,  352. 

Nessler  reagent,  Exp.  70. 

Neutral  salts,  170. 

Newton's  metal,  256. 

Nickel,  379. 

Niobium,  260. 

Nicre,  282. 

"     Chili,  271,  b. 
Nitric  acid,  73. 

"  anhydride,  89. 
Nitrocellulose,  230,  b. 
Nitrogen,  50. 

"         chloride,  113. 

group,  257  ;  261,  a. 

"         hydride,  66. 

"         iodide,  119. 

u         oxides,  79-91. 
Nitro-hydrochloric  acid,  114, 
Nitro-muriatic  acid,  114. 
Nitrosyl,  83. 
Nitrous  anhydride,  86. 
Nitryl,  87. 

Noble  metals,  Note,  p.  313. 
Non-metals,  261. 
Nomenclature,  58-60. 
Nordhausen  acid,  156. 
Normal  salts,  170. 
Norwegium,  App.  i. 
O 
Occlusion  of  gases,  24,  3,  d. 


Oil  of  the  Dutch  Chemists,  Exp.  209. 

u     vitriol,  151. 
OJefiant  gas,  217. 
Onyx,  232,  a. 
Opal,  232,  a. 
Organic  chemistry.  222. 

'*       substances,  7,  222. 
Ornithorhyncus,  The  metallic,  377,  b. 
Orpiment,  250. 
Orthoboric  acid,  173. 
Osmiridium,'  404. 
Osmium,  404. 
Ossein,  224. 
Oxalic  acid,  Exp.  289. 
Oxides,  33. 
Oxygen,  16,  29. 

"        Linking,  163,  c. 

"        Preparation  of,  30. 

"       Properties  of,  32,  33. 

"       Relation  to  animal  life,  35. 

"       salts,  171. 

"       Saturating,  163,  c. 

"       Tests  for,  36. 

"       Uses  of,  34. 
Oxyhydrogen  flame,  41. 
Oyster  shells,  293. 
Ozone,  37. 


Painter's  colic,  315. 

Palladium,  400. 

Paraffin,  138,  e. 

Parchment,  Vegetable,  Exp.  216. 

Paris  green,  324. 

Paste,  234,  d. 

Pearlash,  278. 

Peat,  181. 

Pentad,  92,  a. 

Percentage  computations,  13*. 

Permanganic  acid,  376,  f. 

Pewter,  388,  a, 

Philosopher's  candle,  Exp.  26. 

Phosgene  gas,  194,  b. 

Phosphine,  240. 

Phosphoric  sun,  Exp.  37. 

Phosphorus,  235. 

acids,  242. 

hydride,  240. 

oxides,  241,  Exp.  58. 
"  Red,  238. 


INDEX. 


351 


Figures  refer  to  Paragraphs, 

Phosphoryl,  242,  d. 
Phosphurets,  Note,  p.  205. 
Phosphuretted  hydrogen.  240. 
Photography,  Note,  p.  269. 
Physical  changes,  10. 
Pig  iron,  358. 
Pinch  cocks,  App.  20. 
Pipettes,  App.  5. 
Plaster  of  Paris,  294. 
Plate  glass,  234,  b. 
Platinum,  397. 

"         black,  398,  d. 

"         sponge,  398,  c. 
Plumbago,  179. 
Plumbic,  see  Lead, 
Plumbous,  see  Lead. 
Pneumatic  trough,  App.  12. 
Polymerism,  216. 
Potash,  278. 
Potassium,  272. 

"          bicarbonate,  279. 

"          carbonate,  278. 

"          chlorate,  281. 

"         chloride,  276. 

"          chrotnate,  381,  c, 

"          cyanide,  277. 

14          dichromate,  381,  c, 

"          ferricyanide,  368. 

11          ferrocyanide,  368. 

"          hydrate,  280. 

"          nitrate,  282. 

"          oxides,  275. 

tartrate,  273,  a. 
Precipitated  silica,  Exp.  217. 
Precipitate,  Red,  339. 
Products,  126. 

Proportions,  Law  of  definite,  90. 
Law  of  multiple,  91. 
Prussian  blue,  368. 
Prussic  acid,  205. 
Puddling  furnace,  360,  a. 
Pyroboric  acid,  173,  b. 
Pyroligneous  acid,  215. 
Pyrophosphoric  acid,  242. 
Pyrite,  131,  a  ;  364. 
Pyroxylin,  230,  b. 


Quadrantoxide,  323. 
Quadrivalent,  92,  a. 


unless  otherwise  specified. 

Quantitative  analysis,  Note,  p.  296. 
Quantivalence,  92  ;  341,  a. 
Quartz,  232. 
Quicklime,  290. 
Quicksilver,  334. 
Quinquivalent,  92,  a. 

R 

Radicals,  97. 

Rational  symbols,  94,  216,  b. 

Reactions,  124,  125. 

Reagents,  124. 

Realgar,  250. 

Red  lead,  312. 

"    oxide  of  manganese,  376,  b. 

"    oxide  of  mercury,  339. 

"    phosphorus,  238. 

"    precipitate,  339. 

"    prussiate  of  potash,  368. 
Reduction  of  oxides,  Exp.  31. 
Red  zinc  ore,  301,  304. 
Regent  diamond,  178,  a. 
Retorts,  App.  7  and  22. 
Retort  stands,  App.  10. 
Rhodium,  401. 
Rochelle  salt,  269,  a. 
Rock  crystal,  232. 

"      salt,  266. 
Rose  quartz,  232,  a. 
Rose's  metal,  256. 
Rouge,  Jeweller's,  362,  b. 
Rubidium,  284. 
Ruby,  348. 

"      copper,  323. 
glass,  395,  a. 
Ruthenium,  403. 


Sago,  228. 
Sal-ammoniac,  287. 
Saleratus,  279. 
Salsoda,  268. 
Salt,  266. 

"    Epsom,  300. 

"    Glauber,  267,  b. 

"    of  tartar,  278. 

"    Rochelle,  269,  «. 
Saltpetre,  282. 

"         South  American,  271,  b, 
Salts  classified,  170. 


352 


INDEX. 


Figures  refer  to  Paragraphs,  unless  otherwise  specified.' 


Salts  defined,  169. 

"    Nomenclature  of,  60. 

"    Sulphur,  171. 
Sand,  232,  a. 

"      bath,  74,  a  \  App.  10. 
Sapphire,  348. 
Scale  oxide,  362,  c. 
Scrubber,  221,  h. 
Selenite,  294. 
Selenium,  160. 
Septivaleut,  92,  a. 
Serpentine,  381. 
Sesqui —  143,  a, 
Sexivalent,  92,  a. 
Shells,  293. 

Siemens-Martin  steel,  372. 
Silica,  232. 
Silicic  acid,  Exp.  217. 

"     anhydride,  232. 
Silicon,  231. 
Silver,  325. 

"      bromide,  330. 

"      carbonate,  333. 

"      chloride,  330. 

"      cyanide,  331. 

"      Fulminating,  329. 

"      German,  303,  a. 

"      haloids,  330. 

"      Horn,  330. 

"      iodide,  330. 

"      nitrate,  332. 

"      oxides,  329. 

"      phosphate,  333. 

"      sulphate,  333. 

"      sulphide,  331. 
Simple  radicals,  97. 
Slag, 359- 

Slaked  lime,  290,  c  ;  292. 
Smithsonite,  301. 
Soap,  Hard,  270 ;  278,  6. 

Lime,  292,  a. 
"     Soft,  278,  b  ;  280. 
Soda,  269. 

"     ash,  268,  a. 

u     Caustic,  270. 
"     Cooking,  269. 
"     crystals,  268,  b. 

"      Washing,  268,  b. 
"     water,  199. 
Sodium,  262. 


Sodium  biborate,  271. 

"       bicarbonate,  269. 

"       bisulphate,  267,  c. 

11       carbonate,  268. 

"       chloride,  266. 

"       hydrate,  270. 

u       nitrate,  271. 

"       oxides,  265. 

"       pjrroborate,  271. 

"       sulphate,  267. 
Soft  coal,  181. 
a    soap,  278,  b  ;  280. 
"   water,  294. 
Solder,  388,  a. 
Soldering,  App.  18. 
Soluble  glass,  234. 
Solution,  9,  a. 
Soot,  185. 

South  American  nitre  or  saltpeter,  271, 
Spathic  iron,  354,  a. 
Specular  iron,  354,  a. 
Spelter,  302,  d. 
Sphalerite,  301. 
Spiegeleisen,  359,  d. 
Stalactite,  293. 
Stalagmite,  293. 
Stannic,  see  Tin. 
Stannous,  see  Tin. 
Starch,  228. 

"      sugar,  227. 

"      test  for  iodine,  Note,  p.  99. 
Stassfurt,  276,  298. 
Steel,  369-373- 
Stibine,  253. 
Stibnite,  251. 

Stoichiometry,  Note,  p.  108. 
Stop-cocks,  App.  20. 
Strass,  234,  d. 
Strontianite,  296. 
Strontium,  296. 
Suboxide  of  mercury,  339. 

"        of  copper,  323. 
Sucrose,  226. 
Suffioni,  173. 
Sugar,  225-227. 

"      of  lead,  314. 
Sulphur,  131. 

"       acids,  149,  151,  157. 

u       group,  162. 

"       Linking,  171. 


INDEX. 


353 


Figures  refer  to  Paragraphs,  unless  otherwise  specified. 


Sulphur  oxides,  143,  150,  157. 

"        salts.  171. 

"       Saturating,  171. 
Sulphuret,  Note,  p.  115. 
Sulphuretted  hydrogen,  137. 
Sulphuric  acid,  151. 

"         ether,  213. 
Supporters  of  combustion,  43. 
Symbols,  56,  57,  93-96,  261,  c. 
Synthesis  defined,  18. 

"        of  water,  17. 

T 

Table  salt,  266. 

Tantalum,  259. 

Tapioca,  228. 

Tar,  Coal,  221,  c. 

Tartar,  Salt  of,  278. 

Tellurium,  161. 

Terbium,  353. 

Ternary  compounds,  Nomenclature  of, 

60. 
Test  papers,  App.  24. 

"    tubes,  App.  4,  d ;  App.  7. 
Tetrad,  92,  a. 
Tetrantoxide,  323,  329. 
Tetravalent,  see  Quadrivalent. 
Thallium,  317. 
Thermometers,  App.  3. 
Thionic  acids,  158. 
Thoria,  392. 
Thorium,  392. 
Tin,  385. 

Adulterations  of,  388,  b. 

compounds,  389. 

oxide,  389. 

stone,  385. 

ware,  Exp.  296. 
Titanium,  390. 
Toluol,  221,  c. 
Topaz,  344. 

Toughened  glass,  234,  g* 
Travertine,  293. 
Triad,  92,  a. 

Trimorphous,  Note,  p.  113. 
Trivalent,  92,  a. 
Tubing,  App.  4,  a. 
Tufa,  293. 
Tungsten,  383. 
Tungstic  acid,  383. 
Turpentine,  Exp.  93. 


Tuyeres,  359. 
Types,  96. 

Typical  symbols,  96. 

=> 

U 

Unit  volume,  175. 
Univalent,  92,  a. 
Uranium,  384. 
Uranyl,  384. 
U-tubes,  App.  4,  b. 


Valence,  92,  d. 

Vanadium,  258. 

Vegetable  parchment,  Exp.  216. 

Ventilating  chamber,  App.  23. 

Ventilation,  194,  199. 

Verdigris,  215,  c  ;  324. 

Vermillion,  340. 

Vinegar,  215. 

Vital  air,  35. 

Vitriol,  Blue,  324. 

"       Green,  367. 

"       Oil  of,  151. 

"       White,  304. 
Volatile  alkali,  168. 
Volumetric  combination.  Law  of,  176. 
"          computations,  129. 

W 

Wash  bottle,  App.  8. 
Washing  soda,  268,  b. 
Water,  Analysis  of,  14. 

"      bath,  App.  10. 

"      composition  of,  14, 17,  40, 

"      glass,  234. 

Hard  and  soft,  294. 

u      of  crystallization,  268,  c. 

"      synthesis  of,  17. 

"      type,  96. 
White  arsenic,  247. 

"     lead,  314. 

"      vitriol,  304. 
Window-glass,  234,  b. 
Wood's  metal,  256. 
Woulffe  bottle,  Note,  p.  23  ;  App.  6. 


Yellow  chromate  of  potash,  381,  c. 


354 


INDEX. 


Figures  refer  to  Paragraphs,  unless  otherwise  specified. 


Yellow  prussiate  of  potash,  368. 
Yttrium,  353. 


Zinc,  301. 

"    carbonate,  301. 
u    chloride,  304. 
''    dust,  302,  c. 
"    ore,  301. 


Zinc  oxide,  304. 

"    silicate,  301. 

"    spar,  301. 

"    sulphate,  304. 

"    sulphide,  301. 

"    white,  304. 
Zincite,  301. 
Zirconia,  391. 
Zirconium,  391. 


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Sheldon  £ 

Company's 

Text-Books. 

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ental  Philosophy.     1  vol.  12mo 

Including  the  Intellect,  the  Sensibilities,  and  the  Will.  '  B/y^ 
FOSEPH  HAVEN,   Professor  of  Intellectual  and  Moral  Phil<4- 
>phy,  Chicago  University. 

It  is  believed  this  work  will  be  found  pre-eminently  distinguished  for  ; 
he  completeness  with  which  it  presents  the  whole  subject, 

/  i 

oral  Plillosoplnj . 

Including  Theoretical  and  Practical  Ethics.  By  JOSEPH 
1  AVEN,  D.D.,  late  Professor  of  Moral  and  Intellectual  Philos- 
>phy  i  r 


Istoi 

By 

The 
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THE  UNIVERSITY  OF  CALIFORNIA  LIBRARY 


-     -   •    ;.a:ni  JsC.i'l'WH  '.UUW  LUlilplLLL;.    iuu  LULLI^  uiuu  umi   i 
K-ai  Liatin-English  and  English-Latin  Lexicon  published     1  vol. 
•oyal  octavo,  about  1400  pages. 
7e  recently  published  a  copious  and  critical  Latin-English  Dictionary,  for  ' 

u*e  of  schools-  etc.,  abridged  and  re-arranged  from  Riddle' s  Latin-Engli^u 
ricon,  founded  on  the  German-Latin  Dictionaries  of  Dr.  Wm.  Freund  and   : 
ers,  by  R-?v.  P.  BTTLLIONS,  D.D.,  author  of  the  series  of  Grammars,  English, 
in,  an--'  ' '>>?ek,  oa  the  pume  plan,  etc.,  etc.,  to  which  we  have  now  added  an  i 
^lish-Lar.v.  Dl^t 'nary,  making  together  the  most  useful  and  convenient,  at 

hitme  ti;;.--  the  cheapest  Latin  Lexicon  published. 


I 


